A Level Chemistry Booklet (OCR B Salters) 2025 PDF
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This is a Chemistry booklet for an A-level OCR B Salters course, focused on the "Elements of Life Pt1" topic and covering numerous sub-topics like atomic structure, isotopes, molar calculations, bonding, and molecular shapes. It includes learning sequences, powerful knowledge sections, and practice questions.
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Chemistry Booklet A Level OCR B Salters H033 1. Elements of Life Pt1 Name: ____________________________________________ Class: _____________________________________________ Teacher: __________________________________________ Table of Contents Data sheet..................................
Chemistry Booklet A Level OCR B Salters H033 1. Elements of Life Pt1 Name: ____________________________________________ Class: _____________________________________________ Teacher: __________________________________________ Table of Contents Data sheet............................................................................................................................................................. 1 Common ions relevant to the topic...................................................................................................................... 3 Learning Sequence 1: Formulae and equations................................................................................................... 4 Powerful knowledge: Atomic structure............................................................................................................ 4 Independent practice; Atomic structure...................................................................................................... 5 Powerful knowledge: Isotopes......................................................................................................................... 6 Powerful knowledge: Mass spectroscopy........................................................................................................ 7 Powerful knowledge: Calculating average atomic mass of isotopes............................................................... 9 Powerful knowledge: Avogadro’s number (NA)............................................................................................. 13 Powerful knowledge: Empirical formula........................................................................................................ 15 Independent practice..................................................................................................................................... 17 Learning Sequence 2: Electron arrangement in atoms...................................................................................... 22 Powerful knowledge: Electron shells, orbitals and subshells......................................................................... 22 Powerful knowledge: Evidence for atomic structure..................................................................................... 26 Comprehension task: Trends in first ionisation energy.............................................................................. 28 Powerful knowledge: Nuclear fusion............................................................................................................. 29 Think, pair, share........................................................................................................................................ 30 Independent practice..................................................................................................................................... 30 Learning Sequence 3: Bonding and structure.................................................................................................... 34 Powerful knowledge: Covalent bonding........................................................................................................ 34 Dative covalent bonds................................................................................................................................ 35 Powerful knowledge: Ionic bonding............................................................................................................... 38 Anions and cations..................................................................................................................................... 39 Powerful knowledge: Metallic bonding.......................................................................................................... 43 Powerful knowledge: Structure and Properties of Simple Molecular Structures.......................................... 43 Powerful knowledge: Structure and Properties of Giant Covalent Structures.............................................. 44 Powerful knowledge: Structure and Properties of Ionic Compounds............................................................ 45 Powerful knowledge: Structure and Properties of Metallic Structures......................................................... 46 Powerful knowledge: Shapes of molecules.................................................................................................... 50 Powerful knowledge: Bonding pairs and no lone pairs.................................................................................. 50 Task: Molecule shapes................................................................................................................................ 50 Powerful knowledge: Bonding Pairs and Lone Pairs of Electrons.................................................................. 52 Independent practice..................................................................................................................................... 55 Learning Sequence 4: Amount of substances and chemical calculations.......................................................... 58 Powerful knowledge: Number of Moles........................................................................................................ 58 Powerful knowledge: Molar calculations....................................................................................................... 59 Powerful knowledge: Percentage composition.............................................................................................. 63 Powerful knowledge: Percentage yield.......................................................................................................... 66 Powerful knowledge: Water of crystallisation............................................................................................... 72 Independent practice..................................................................................................................................... 75 Data sheet 1 2 Common ions relevant to the topic Ion formula Ion name Nitrate Sulphate Carbonate Hydroxide Ammonium Hydrogen carbonate Copper (II) Zinc ion Lead (II) Iron (II) Iron (III) Silver ion 3 Learning Sequence 1: Formulae and equations Outcomes: Describe the structure of atoms and isotopes. Describe how mass spectroscopy can be used to determine the abundance of different isotopes. Calculate the atomic mass of elements from mas spectroscopy data. Make use of Avogadro’s number to calculate chemical quantities per mole. Powerful knowledge: Atomic structure Atoms are made up of protons, neutrons and electrons which are located in different locations of the atom and have unique masses and charges. Task: Complete the table below to show the relative mass and charges of the subatomic particles. Subatomic particle relative mass charge proton neutron electron The nucleus is at the center of the atom and contains the protons and neutrons. Protons and neutrons are collectively known as nucleons. The atomic number is unique to different elements and determines what the element is, for example only carbon has 6 protons hence an atomic number of 6. Number of protons = ATOMIC NUMBER of the atom The total number of protons and neutrons is known as the atom’s mass number or its relative atomic mass (Ar). It is how heavy the atom is. 4 Number of protons + number of neutrons = MASS NUMBER of the atom The number of electrons in an elemental atom is equal to the number of protons and hence an elemental atom has a net charge of 0. This information can be given in the form: Independent practice; Atomic structure Using your periodic table, answer the questions below: 1. How many protons are in an atom of Fluorine? _________________________________________________________________________ _________________________________________________________________________ 2. How many electrons are in an atom of Fluorine? _________________________________________________________________________ _________________________________________________________________________ 3. How many neutrons are in an atom of Fluorine? _________________________________________________________________________ _________________________________________________________________________ 5 Powerful knowledge: Isotopes The number of neutrons in an atom can vary. For example, there are three kinds of carbon atoms (isotopes) 12C, 13C and 14C. They all have the same number of protons, but the number of neutrons varies. Isotopes have the same number of electrons and thus will react in the same way as each other as it is the electrons that affect how they react. I do: Calculate the number of protons, electrons and neutrons in an atom of carbon-12 ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ We do: Calculate the number of protons, electrons and neutrons in an atom of carbon-13 ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ You do: Calculate the number of protons, electrons and neutrons in an atom of carbon-14 ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 6 Powerful knowledge: Mass spectroscopy The mass of atoms can be determined using mass spectroscopy. The atoms are vaporised before being bombarded with electrons to remove electrons from them before they are accelerated towards a detector that will work out their mass and abundance. Mass spectroscopy is carried out in a mass spectrometer like the one below. a. Ionisation Involves removal of a single electron from a vaporised sample of the atoms to result in positive ions with a charge of +1. b. Acceleration Charged plates are used to transfer kinetic energy to the positively charged ions down the mass spectrometer as soon as the positive ions are formed. The larger the mass of the ion, the less speed it will have. c. Deflection An electromagnet is used to deflect the positive ions. The larger the ion’s m/z (mass/charge) ratio the less it will be deflected by the electromagnet and will be detected separately to ions with smaller m/z ratio. d. Detection A detector is used to measure the m/z ratio of ions reaching the end of the mass spectrometer as well as their relative abundances compared to other ions being detected. 7 The mass spectrum produced gives an indication of the m/z value as well as the abundance of each mass ion. We/ You do 1. Which of these ions will reach the detector first? Explain your answer. 79Br+ or 81Br+ Explanation: ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 8 2. The mass spectrum of the element gallium (Ga) is shown. Identify the ion responsible for the peak at: m/z 69.0 ______________ m/z 71.0 ______________ Powerful knowledge: Calculating average atomic mass of isotopes The average atomic mass of elements is a weighted average atomic mass based on isotopic masses and their natural abundance. The relative atomic mass of an element can be calculated if the abundances and masses of all its isotopes are known using the formula below. (𝑚1 𝑥 𝑎1) + (𝑚2 𝑥 𝑎2) + ⋯ 𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑎𝑡𝑜𝑚𝑖𝑐 𝑚𝑎𝑠𝑠 = (𝑎1 + 𝑎2 + ⋯ ) Where: m1 is the mass of isotope 1, and a1 is the abundance of isotope 1. 9 I do: Calculate the relative atomic mass of Chlorine if it exists as two isotopes Cl-37 and Cl-35 with an abundance of 25% and 75% respectively. ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ We do: Bromine has two isotopes Br-79 and Br-81, use your periodic table to calculate the abundances of the two isotopes. ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ You do 1. Neon has three isotopes, with mass numbers 20, 21 and 22. The relative abundance percentage for each neon isotope is 90.9, 0.26 and 8.8 respectively. Calculate the average atomic mass of neon. __________________________________________________________________________ __________________________________________________________________________ 10 __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2. Gallium has two isotopes. 60% of gallium atoms have a mass of 69 and 40% have a mass of 71. Calculate the relative atomic mass (Ar) of gallium. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 3. Calculate the relative atomic mass of zirconium given that 52% of atoms have a mass of 90, 11% have a mass of 91, 17% have a mass of 92, 17% have a mass of 94 and 3% have a mass of 96. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 11 4. The mass spectrum of a sample of gallium is shown. a. What isotopes are present in this element? ________________________________________________________________________ ________________________________________________________________________ b. Calculate the relative atomic mass of this element. Give your answer to the appropriate number of significant figures. Show your working. ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ 12 Powerful knowledge: Avogadro’s number (NA) Avogadro’s number is the number of atoms or molecules in one mole of a substance, which is equal to 6.023 × 1023. The number of moles in a given mass can be calculated by the formula: 𝑚𝑎𝑠𝑠 (𝑔) 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠 = 𝑀𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 I do 1. Calculate the number of atoms in 18g of water. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2. Calculate the number of molecules of oxygen in 10g of oxygen. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ We do 1. Calculate the number of carbon atoms in 5g of ethane (C2H6) __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 13 You do 1. Calculate the number of molecules of ethane in 2g of ethane. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2. Calculate the number of atoms of hydrogen in 16g of sulphuric acid (H2SO4) __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 3. Calculate the number of oxygen atoms in one mole of oxygen. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 14 Powerful knowledge: Empirical formula It is the simplest whole number ratio of elements in a compound. For example, ethene has the molecular formula C2H4 but the empirical formula CH2. I do 1. A compound is found to contain 23.3% magnesium, 30.7% sulphur, and 46.0% oxygen. What is the empirical formula of this compound? __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2. What is the empirical formula of a compound containing 60.0% sulphur and 40.0% oxygen by mass? __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 15 We do 1. A sample of an oxide of nitrogen is found to contain 30.4% nitrogen. What is its empirical formula? ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ You do 1. What is the empirical formula of a compound containing 47.37% carbon, 10.59% hydrogen, and 42.04% oxygen? ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 2. Find the empirical formula for a compound containing 40.6% carbon, 5.1% hydrogen, and 54.2% oxygen. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 16 Independent practice 1(a). Scientists study the atomic emission spectrum of the Sun to find out about its composition. Complete Table 23.1 for atoms of the isotopes of helium. 3He 4He atomic number number of electrons number of neutrons mass number Table 23.1 (b). Titanium is an element formed by nuclear fusion. i. Table 23.2 shows the stable isotopes of titanium and their abundances. Isotope 46Ti 47Ti 48Ti 49Ti 50Ti Percentage abundance 8.25 7.44 73.72 5.41 5.18 Table 23.2 Calculate the relative atomic mass of titanium from these data. Give your answer to 2 decimal places. relative atomic mass =......................................................... 17 2. Naturally occurring carbon consists of two isotopes, carbon-13 and carbon-12. The presence of these can be shown by mass spectrometry. Naturally occurring carbon has 1.1% of carbon-13. i. Calculate the relative atomic mass of naturally occurring carbon. Give your answer to 2 decimal places. relative atomic mass =.......................................................... ii. A molecule consists of two carbon atoms. It has a visible ‘M+1’ peak but no visible ‘M+2’ peak in its mass spectrum. Suggest why. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 18 3. The element indium was discovered in 1863 from an emission spectrum. Indium has two naturally occurring isotopes as shown in the table. Isotope Isotopic mass 113In 112.90 115In 114.90 The relative atomic mass, Ar, of indium is 114.82. Calculate the percentage abundances of the two isotopes. 113In.............. %; 115In.............. % 4. The presence of chlorine in organic compounds can be seen from their mass spectra. Chlorine has two isotopes in the proportions as shown. 35Cl 75.53% 37Cl 24.47% Calculate a value for the Ar of chlorine. Give your answer to two decimal places. Ar =......................................... 19 5. Naturally occurring silicon has three isotopes, as shown in the table. Isotope Si-28 Si-29 Si-30 % abundance 92.17 4.71 3.12 Calculate an Ar value for Si from these data, showing your working. Give your answer to two decimal places. Ar =........................................................... 6. Analysis of a sample of boron by a time-of-flight mass spectrometer produced the following mass spectrum. i. What information is given by the height of the two peaks on the mass spectrum? ___________________________________________________________________________ ___________________________________________________________________________ 20 ii. Explain how the information given on a mass spectrum, such as the one shown above for boron, can be used to calculate the relative atomic mass of an element. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ iii. A key stage in the operation of a time-of-flight mass spectrometer is the acceleration of positive ions. Explain how this process allows the instrument to separate ions of different masses. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 21 Learning Sequence 2: Electron arrangement in atoms Outcomes Describe the arrangements of electrons in atoms in terms of shells, subshells and orbitals. Write electronic configuration of atoms using s, p, d, f and box notation. Describe the Giger-Marsden experiment and first ionisation energies as evidence for the structure of the atom and distribution of electrons within them. Write balanced nuclear fusion reactions. Connect EL – Structure of the atom Powerful knowledge: Electron shells, orbitals and subshells Electrons are arranged around the atom in shells which have a distinct energy level. The further away from the nucleus the shell is the higher the energy of the electrons in them. Each shell will hold a defined number of electrons. The shells can be further divided into sub-shells which hold a defined number of electrons. The sub-shells can also be divided into orbitals which have a distinct shape. Shell Sub-shells Number of electrons held in shell 1 1s 2 2 2s 2p 8 3 3s 3p 3d 18 4 4s 4p 4d 4f 32 22 There is 1 s orbital in a s subshell; there are 3 p orbitals in a p subshell; there are 5 d orbitals in a d subshell and there are 7 f orbitals in a f subshell. An Orbital holds electrons in pairs with opposite spin. Each sub-shell can hold a maximum number of electrons. Sub-shell Number Maximum number of Shape of orbital orbitals electrons held in sub- shell s 1 2 Spherical p 3 6 Dumbbell d 5 10 f 7 14 Electrons arrange in atoms from the first shell in the order s-p-d-f until all the electrons are used up. The 4s orbital fills up before the 3d orbitals because the 4s orbital is at a lower energy level than the 3d orbitals. I do 23 1. Write down the electronic configuration of an atom of iron using: i. shells and orbitals ________________________________________________________________________ ii. the box model. ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ We do 1. Write down the electronic configuration of an atom of sodium using: i. shells and orbitals ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ii. the box model ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ 24 2. Write down the electronic configuration of an ion of sulphur (S2-) using: i. shells and orbitals ________________________________________________________________________ ________________________________________________________________________ ii. the box model ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ You do 1. Write down the electronic configuration of an atom of Calcium using: i. shells and orbitals ________________________________________________________________________ ________________________________________________________________________ ii. the box model ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ 25 ________________________________________________________________________ 2. Write down the electronic configuration of an ion of Zn2+ using: i. shells and orbitals ________________________________________________________________________ ________________________________________________________________________ ii. the box model ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ Powerful knowledge: Evidence for atomic structure i. The Geiger-Marsden experiment (1909 - 1911) Hans Geiger and Ernest Marsden tested the plum pudding model. They aimed beams of positively charged particles at very thin gold foil. These particles should have passed straight through, according to the plum pudding model. However, many of them changed direction. Ernest Rutherford explained these results in his ‘planetary model’: atoms have a central, positively charged nucleus with most of the mass. electrons orbit the nucleus, like planets around a star. ii. Ionisation energies The ionisation energy of an atom is the amount of energy needed to remove one electron from a mole of gaseous atoms. X (g) → X+ (g) + e- (g) 26 There are three main factors that affect first ionisation energies: Factor Effect on first ionisation energy Increasing nuclear charge Increasing atomic radius Increasing electron shielding 27 Comprehension task: Trends in first ionisation energy 1. The first ionisation energy (increases/ decreases) across the period due to an (increase/ decrease) in ________________________________________________________________ ____________________________________________________________across the period. 2. The first ionisation energy (increase/ decreases) down groups due to __________________ __________________________________________________________________________ ____ and __________________________________________________________________ ____________________________ resulting in lower attraction of the outer shell electrons to the nucleus. I do: For the pairs of atoms below, explain which one will have a lower first ionisation energy and why. 1. Lithium and Carbon ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 28 2. Beryllium and Magnesium ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ We do 1. Chlorine and Boron ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ You do 1. Calcium and Silicon ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ Powerful knowledge: Nuclear fusion Nuclear fusion is the joining of two light nuclei to form a larger single nucleus. Usually, a single neutron is formed alongside the heavier nucleus. Due to the high repulsion between the two positive nuclei a lot of energy and pressure is 29 needed to force the nuclei together. The right conditions for this to occur are only found in the core of the sun. Nuclear fusion can be shown using nuclear equations; Think, pair, share 1. Complete the fusion reaction below: 2 3 1𝐻 + 1𝐻 → _______ + 10𝑛 2. Explain the term ‘nuclear fusion’ and why the pressure and temperature have to be very high for nuclear fusion to occur. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ Independent practice 1. Which of these electron distributions is correct for an oxygen atom? Your answer 30 2. Element W is in Group 17 of the Periodic Table and element X is in Group 2. What is correct? A The outer sub-shell electron configuration of W is p5. B The outer sub-shell electron configuration of X is p2. C W and X react to form the compound WX 2. D X has 5 more electrons than W. Your answer 3. Boron has electron configuration 1s22s22p1. Which statement is correct for a boron atom? A Each s-orbital contains 1 electron. B It has three sub-shells that contain electrons. C It has three unpaired electrons. D It has two orbitals. Your answer 4. What provided evidence of the atomic nucleus? A Thomson’s discovery that all elements contain electrons. B Geiger and Marsden firing α-particles at gold leaf. C The magnitude of successive ionisation energies. D The lines on an atomic emission spectrum. Your answer 31 5. A student is investigating the properties of some s-block metals and their compounds. Complete the electronic configuration, using sub-shells, of an atom of sodium and the magnesium ion in magnesium carbonate. sodium atom 1s2.............................................................. magnesium ion 1s2.............................................................. 6. Many of the chemical elements found on Earth were produced in nuclear fusion reactions in stars. Write a nuclear equation to show the fusion of the nuclei of two hydrogen-2 atoms to give a single atom. 7. i. Complete the electron configuration of gallium, Ga. 1s22s22p63s23p6_______________________________ ii. Describe the shape of an s-orbital. ___________________________________________________________________________ ___________________________________________________________________________ 32 iii. Give the charge on the cation of gallium predicted by its position in the Periodic Table. ___________________________________________________________________________ ___________________________________________________________________________ 8. ‘Silicon burning’ is a fusion process that occurs in stars just before they collapse. Each silicon nucleus, mass number 28, fuses with seven helium nuclei (42He) one after the other. The final product is an isotope of nickel. Give the mass number of the nickel isotope produced and the number of protons and neutrons it contains. mass number............................................ protons..................................................... neutrons................................................... 33 Learning Sequence 3: Bonding and structure Outcomes Describe covalent and dative bonding in molecules. Describe ionic and metallic bonding using ideas about ions. Describe the physical properties of simple molecules, giant covalent structures, ionic lattice and metallic structures. Use electron bond repulsion theory to explain the shapes and bond angles in simple molecules. Connect GCSE- Bonding Powerful knowledge: Covalent bonding Covalent bonds are formed when non-metals react with other non-metals. They will share pair(s) of electrons with the other non-metal to adopt a group 0 number of electrons in the outer shell. Group of elements 4 5 6 7 Pairs of electrons shared 4 3 2 1 Hydrogen will form one covalent bond to adopt the same number of electrons in its outer shell- like Helium thereby gaining stability. The covalent bond is the balance between the attraction between the shared electrons and the two nuclei and the repulsion between the two nuclei. The bond is most stable when the distance between the two nuclei is such that attraction and repulsion forces are balanced. This distance is known as the bond length. 34 Dative covalent bonds Dative bonds occur when one atom in a molecule provides both electrons for sharing in the covalent bond with another atom. The atom providing the pair of electrons to be shared must have a lone pair of electrons and the atom receiving the electrons must have an empty orbital to accept them. Only one pair of electrons per atom can be used in the formation of a dative bond as two or more electron pairs from the same atom forming a dative bond around a central atom can lead to electron repulsion making the bond highly unstable. I do 1. Draw a dot and cross diagram to show the covalent bonding in silicon dioxide (SiO2). 2. Draw a dot and cross diagram to show the covalent bonding in ammonia (NH3). 35 3. Draw a dot and cross diagram to show the covalent bonding in an ammonium ion (NH4+) We do 1. Draw a dot and cross diagram to show the bonding in a molecule of sulphur hexafluoride (SF6). 2. Draw a dot and cross diagram to show the covalent bonding in water. 36 3. Draw a dot and cross diagram to show the covalent bonding in a hydronium (H3O+) ion. You do 1. Define the term: covalent bond and compare it to a dative bond. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2. Draw a dot and cross diagram to show the covalent bonding in ethane. 37 3. Draw a dot and cross diagram to show the bonding in boron trifluoride (BF3) 4. Draw a dot and cross diagram to show the bonding in sulphur trioxide (SO3) Powerful knowledge: Ionic bonding Ionic bonds are formed when metals and non-metals react. Metals usually _______________ one or more electrons to form stable ______________ (positively charged ions). Non-metals usually ________________ one or more electrons to form stable ______________ (negatively charged ions). 38 The ionic bond is the overall electrostatic attraction in a lattice and is made up of attraction between ions of different charge and repulsion between ions of the same charge. Group 1 2 3 6 7 Charge on ion +1 +2 +3 -2 -1 formed Anions and cations The charge on ions can be predicted from the element’s position in the Periodic Table. H+ He Li+ Be B C N3- O2- F- Ne Na+ Mg2+ Al3+ Si P S2- Cl- Ar K+ Ca2+ Br- Kr Rb+ Sr2+ I- Xe Cs+ Ba2+ I do 1. Work out the formula of magnesium chloride. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 39 2. Work out the formula of sodium sulphide. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 3. Draw a dot and cross diagram to show the bonding in magnesium bromide. We do 1. Work out the formula of aluminum chloride. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2. Draw a dot and cross diagram to show the bonding in calcium sulphide. 40 You do 1. Complete the table below: Ionic compound Cation (positively Anion (negatively Formula charged ion) charged ion) sodium chloride MgO Li+ S2- CaCl2 Cs+ Br- aluminium oxide Mg2+ N3- 2. Draw dot-and-cross diagrams for the following: (a) magnesium oxide 41 (b) Lithium sulfide (c) Calcium chloride (d) Aluminum oxide 42 (e) Magnesium nitride Powerful knowledge: Metallic bonding In a metal element, the outer main levels of the atoms merge so that there is a lattice of positive ions existing in a ‘sea’ of delocalised outer electrons. The number of delocalised electrons depends on how many electrons have been lost by each metal atom. The metallic bonding spreads throughout so metals have giant structures. Powerful knowledge: Structure and Properties of Simple Molecular Structures BONDING Covalent bonds with shared pair(s) of electrons STRUCTURE Simple molecular Simple molecular structures have low melting temperatures Gases, liquids, and solids with molecular structures have strong covalent bonds between the atoms (intramolecular) only, not between the molecules (intermolecular). There is only weak attraction between the molecules, so they need little energy to move apart from each other. Simple molecular structures are poor conductors of electricity The molecules are neutral overall so there are no charged particles to carry the current even if 43 they dissolve in water. Some covalent compounds react with water to form ions and the resulting solution will conduct electricity. e.g. HCl (g) + H2O (aq) → H3O+ (aq) + Cl- (aq) Powerful knowledge: Structure and Properties of Giant Covalent Structures In some covalent structures, the covalent bonds extend throughout the compound and have the typical property of a giant structure held together with strong bonds – a high melting temperature. BONDING Covalent STRUCTURE Giant Diamond consists of pure carbon with covalent bonding between every carbon atom. The bonds spread throughout the structure which is why it is a giant structure. Each carbon atom is covalently bonded to four other carbon atoms with bond angles of 109.5 ° in a tetrahedral arrangement. Graphite consists of pure carbon with three single covalent bonds between each carbon atom. The bonds spread throughout the structure which is why it’s a giant structure. Each carbon atom is covalently bonded to three other carbon atoms with bond angles of 120°. This leaves a spare electron from each carbon atom which is delocalised throughout the structure allowing it to conduct electricity. There is no covalent bonding between the hexagonal layers of carbon atoms, but they are held together by the weak intermolecular forces allowing the layers to slide across one another 44 making graphite soft and flaky. Macromolecular structures have high melting temperatures Macromolecules have high melting points because they have giant structures with strong covalent bonds. Macromolecular structures are poor conductors of electricity (except graphite) Macromolecules do not have free charged particles to carry charge, so they do not conduct electricity (with the exception of graphite which has delocalized electrons to carry charge). Powerful knowledge: Structure and Properties of Ionic Compounds BONDING Electrostatic attraction between oppositely charged ions STRUCTURE Giant ionic lattice Ionic compounds have high melting points There are strong electrostatic forces of attraction between the positive and negative ions in a giant ionic lattice. The melting point of NaCl is 801˚C. 45 Ionic compounds conduct electricity when melted or dissolved in water Solid ionic compounds do not conduct electricity because the ions cannot move. The ions are held firmly by strong electrostatic forces of attraction in the giant lattice. Ionic compounds are brittle They shatter when given a sharp tap as the lattice is distorted so ions with the same charge come into contact. Powerful knowledge: Structure and Properties of Metallic Structures BONDING Strong metallic bonds STRUCTURE Giant Metallic Structures have high melting temperatures Metals have high melting points because they have giant structures with strong attraction between metal ions and the sea of delocalised electrons. This makes the atoms difficult to separate. Metallic structures are good conductors of electricity The delocalised electrons can move throughout the structure explaining why metals are such good conductors of electricity. Metallic structures are strong Metallic structures are strong with delocalised electrons extending throughout the solid so there are no individual bonds to break. The strength of the bond depends on the charge and the size of the ion. - The greater the charge, the greater the number of delocalised electrons and the 46 stronger the electrostatic attraction between the positive ions and the electrons. - The smaller the ion, the closer the electrons are to the positive nucleus and the stronger the bond. We do – MWB Quiz You do Task: Complete the following model answers for the properties of the four main structure types: 1. Giant Ionic Lattices Bonding: ______________________________________ Example: ______________________________________ Melting and Boiling Points: _______________________ _______________________ electrostatic force of attraction between oppositely charged ions (ionic bonds). A high amount of __________________________ is needed to break these bonds. Electrical Conductivity: Cannot conduct when _________________________ Ions fixed in a lattice, cannot move, cannot carry charge. Can conduct when ______________________________ Ions free to move and carry charge. 47 2. Giant Metallic Lattices Bonding: _________________________________________ Example: _________________________________________ Melting and Boiling Points: __________________________ __________________________ metallic bonds between positive metal ions and delocalised electrons. A high amount of __________________________________ is needed to break these bonds. Electrical Conductivity: Can conduct electricity. _____________________________________________________ free to move and carry charge. 3. Simple Molecular (covalent) Lattices Bonding: ___________________________________ Example: ___________________________________ Melting and Boiling Points: ___________________ ______________ intermolecular forces between molecules. A low amount of _____________________ is needed to break them. 48 Electrical Conductivity: Cannot conduct electricity. No _________________________ or _________________________ to carry charge. 4. Giant Covalent Lattices Bonding: _________________________________________ Example 1: _________________________________________ Melting and Boiling Points: ________________________ Strong _________________________________ bonds between atoms. A high amount of energy is needed to ________________ these bonds. Electrical Conductivity: Cannot conduct electricity. No charge carriers (delocalised electrons or free to move ions). Example 2: _____________________________________ Melting and Boiling Points: _______________________________ Strong __________________________ bonds between atoms. A high amount of energy is needed to _________________ these bonds. Electrical Conductivity: Can conduct electricity. Delocalised electrons are free to move across the layers and carry charge. 49 Powerful knowledge: Shapes of molecules Compounds are 3D in nature. Their exact shape depends on the pairs of bonding and non- bonding electrons around a central atom. The bonding and non-bonding pairs of electrons will repel each other to get as far away from each other resulting in 3D shapes. Powerful knowledge: Bonding pairs and no lone pairs We do: Molecule shapes Make the following molecules using molymod kits: (https://phet.colorado.edu/en/simulations/molecule-shapes) and then complete the table below: Name of Example Dot and cross diagram Number of Bond Displayed formula Shape bonding angle ° with bond angles pairs of electrons Linear BeCl2 Trigonal Planar BF3 50 Tetrahedral CH4 Trigonal PCl5 Bipyramid Octahedral SF6 51 Powerful knowledge: Bonding Pairs and Lone Pairs of Electrons Some molecules have lone pairs (non-bonding pairs) of electrons which affect the shape of the molecule. Ammonia and water are good examples of molecules where lone pairs affect the shape. Non-bonding pairs of electrons will repel more than bonding pairs of electrons. For every non- bonding pair the bond angle decreases by 2.5o. The table below can help determine the shape of some molecules having both bonding pair(s) and non-bonding pair(s) I do: Ammonia Ammonia has _______________; _________ pairs are bonding and ________ pairs are lone pairs. The shape is based on a _____________________ but as it only has __________ bonds it 52 is called a ___________________________________________. The bond angle is reduced to ______________o. Because ______________________________ ______________________________________________________________________________ ______________________________________________________________________________ We do: Water Water has _____________________ pairs of electrons; _________________ pairs are bonding and ____________________ pairs are lone pairs. The shape is based on a _________________________ but as it only has ___________________ bonds it is called a ___________________________ shape. The bond angle is reduced to ___________ °. Because _________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 53 We do: Chlorine Tetrafluoride, ClF4- Chlorine tetrafluoride has _________________________ pairs of electrons; ________________ pairs are bonding and ____________________ pairs are lone pairs. The shape is based on an ___________________ but as it only has ___________________________ bonds it is called a ______________________________ (bonding pairs are in the same plane). The bond angle is ___________________ °. Because ___________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 54 Independent practice 1. This exercise is aimed at testing your understanding about the shapes of simple molecules and ions. The first example has been completed for you to show you what to do. Molecule or Number of Number of Number of Shape Bond angle o ion pairs of bonding pairs lone pairs electrons around central atom H2O 4 2 2 Bent/ V 104.5o SiH4 PF3 SCl2 BBr3 BeCl2 PCl6- NH4+ H3O+ SO2 55 2. What is correct about the structure shown below? A The structure has a negative charge. B The structure has one lone pair. C The structure is linear. D The bond angle is 107°. Your answer 3. A compound has a high melting point and does not conduct electricity when solid or molten. What is the structure of the compound? A Giant covalent network B Giant ionic C Giant metallic D Simple molecular Your answer 4. The element iodine is much less soluble in water than potassium iodide, KI. State the structures of iodine and potassium iodide. Suggest why potassium iodide is more water-soluble than iodine. _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ 56 5. The three-dimensional structure of silicon dioxide can be represented as shown below. The Si-O-Si bonds have a larger angle than the H-O-H bond angle of water. i. State the H-O-H bond angle in a water molecule. ___________________________________________________________________________ ii. Explain the bond angle in water. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 6. Sodium and sodium chloride are both solids at room temperature. Describe the structure and bonding in both solids. _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ 57 Learning Sequence 4: Amount of substances and chemical calculations Outcomes Define the mole. Calculate the number of moles in a given mass of substances. Carry out reacting mass calculations using number of moles. Carry out percentage yield and percentage composition calculations. Connect GCSE – quantitative chemistry Powerful knowledge: Number of Moles One mole is the number of atoms or molecules that equal Avogadro’s number (6.023 × 1023). One mole is also equal to a substance’s formula mass in grams. The number of moles can be calculated by the formula: ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ I do 1. Calculate the number of moles in 50g of CaCO3 __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2. Calculate the mass of 0.125mol of CuO __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 58 We do 1. Calculate the number of moles in 20g of HCl __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2. Calculate the mass of 0.1mol of Fe2O3 __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ You do 1. Calculate the number of moles in 1 drop of water assuming a volume of 0.05cm 3 and a density of 1g/cm3 __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2. Calculate the mass of 4mol of NaCl __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ Powerful knowledge: Molar calculations Balanced chemical equations can be used to calculate the amount of products formed or reactants needed in a given reaction. The ratio in which certain chemicals react together is constant and they always form the same 59 ratio of products. This is called the stoichiometric ratio and can be summarised in a balanced chemical equation. For example: 2H2 + O2 → 2H2O Two moles of hydrogen will react with one mole of oxygen to give two moles of water. If 0.1 moles of hydrogen reacted with 0.05 moles of oxygen they would form 0.1 moles of water. I do 1. If 2.4g of magnesium and 1.6g oxygen react together to form magnesium oxide. Calculate the formula mass of magnesium oxide. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 2. What mass of calcium oxide could be obtained by heating 25g of limestone CaCO3 → CaO + CO2 __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 60 __________________________________________________________________________ __________________________________________________________________________ We do 1. Calculate the mass of magnesium oxide formed when 1.5 g of magnesium is burned in air (oxygen). __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2. In the Thermite reaction, a mixture of iron metal and aluminium oxide is formed when 5.0 g of aluminium powder reacts with excess iron(III) oxide. Calculate the mass of iron formed. Fe2O3 + 2Al → 2Fe + Al2O3 __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ You do 1. What mass of aluminium is required to make 60.0 g of aluminium oxide? 4Al + 3O2 → 2Al2O3 __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 61 __________________________________________________________________________ 2. Calculate the mass of tin(IV) iodide formed when 3.16 g of iodine reacts with excess tin. Sn + 2I2 → SnI4 __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 3. When 5.00 g of crystals of hydrated tin (II) chloride, SnCl2.xH2O, are heated, 4.20 g of anhydrous tin (II) chloride are formed. Calculate the number of molecules of water of crystallisation in SnCl2.xH2O (i.e. the value of x). SnCl2.xH2O → SnCl2 + x H2O __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 62 Powerful knowledge: Percentage composition Percentage composition is the percentage by mass of each element in a compound. To work out percentage composition by mass either the mass or total Ar of the atom of concern is needed. This is then represented as a percentage of either the mass or the Mr of the compound. I do 1. A 27.0 g sample of a compound contains 7.20 g of C, 2.20 g of hydrogen and 17.6 g of oxygen. a. Calculate the percentage composition of the elements in the compound. ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ b. Work out the empirical formula of the compound. ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ 2. Calculate the percentage composition of sodium in sodium azide, NaN 3(s); used in automobile air bags. __________________________________________________________________________ __________________________________________________________________________ 63 __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ We do 1. Calculate the percentage composition of aluminium in aluminium oxide, Al2O3; the naturally occurring mineral corundum. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2. Nitrogen in dopamine, C8H11O2N; a neurotransmitter in the brain __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ You do 1. Calculate the percentage composition of: a. Copper in CuBr2 _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ 64 b. Oxygen in NaOH _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ c. Hydrogen in (NH4)2S _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ 2. A student was asked to find the relative atomic mass of an element X. Crystals of chloride X were known to have a formula of XCl2.6H2O. The student dissolved 2.03g of the crystals in water, and then added an excess of silver nitrate solution to the solution formed. A white precipitate of silver chloride was formed, which was filtered, dried and weighed. 2.78g were formed. Ag+ (aq) + Cl- (aq) → AgCl (s) Calculate: a. The number of moles of silver chloride formed _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ b. The number of moles of X chloride solution (assuming all the chlorine in X chloride in 65 in solution as Cl- (aq) _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ c. The mass of one mole of XCl2.6H2O _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ d. The relative atomic mass of X. _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ Powerful knowledge: Percentage yield It is the percentage ratio of actual yield to the theoretical yield. It is calculated by the formula below. 𝑎𝑐𝑡𝑢𝑎𝑙 𝑦𝑖𝑒𝑙𝑑 𝑥 100 𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑦𝑖𝑒𝑙𝑑 = 𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑦𝑖𝑒𝑙𝑑 The actual yield is the mass of product after carrying out a chemical reaction. The theoretical yield is the calculated mass of product that should be produced using molecular 66 mass calculations. If the actual and theoretical yield are the same, the percent yield is 100%. Usually, percent yield is lower than 100%. Reasons for this can include: i. incomplete reactions, and ii. loss of sample during recovery. Percentage yield can be higher than 100% if impurities are present in the product. I do 1. In an experiment to produce a sample of aspirin, 10g of 2-hydroxybenzoic acid was treated under suitable conditions with 7.5cm3 of ethanoyl chloride (an excess). After purification 11g of aspirin were formed. Calculate the percentage yield. CH3COCl + HOC6H4COOH → CH3COOC6H4COOH + HCl 2-hydroxybenzoic acid aspirin __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 67 __________________________________________________________________________ __________________________________________________________________________ 2. Iron (III) phosphate is reacted with sodium sulfate to make iron (III) sulfate and sodium phosphate. By the reaction: 2FePO4 + 3Na2SO4 → Fe2(SO4)3 + 2Na3PO4 The reaction is performed with 100 grams of iron (III) phosphate and an excess of sodium sulfate. a. If 74.0 grams of iron (III) sulfate are actually made during this reaction, calculate the percent yield. ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ b. Is the answer from part a reasonable? Explain. ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ 68 ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ We do 1. In an experiment to produce a sample of aspirin, 15g of 2-hydroxybenzoic acid was treated under suitable conditions with 7.5cm3 of ethanoyl chloride (an excess). After purification, 6g of aspirin were formed. Calculate the percentage yield. CH3COCl + HOC6H4COOH → CH3COOC6H4COOH + HCl 2-hydroxybenzoic acid aspirin __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2. 20 grams of lithium hydroxide was used to make lithium chloride by the reaction: 69 LiOH + KCl → LiCl + KOH The reaction produced 6 grams of lithium chloride. Calculate the percentage yield. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ You do 1. Chlorobenzene, C6H5Cl, is used in the production of chemicals such as aspirin and dyes. One way that chlorobenzene is prepared is by reacting benzene, C6H6, with chlorine gas according to the following equation: C6H6 (l) + Cl2 (g) → C6H5Cl (s) + HCl (g) 45.6 g of benzene is used in the reaction. If the actual yield is 63.7 g of chlorobenzene, calculate the percentage yield. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 70 __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2. When carbon disulfide burns in the presence of oxygen, sulfur dioxide and carbon dioxide are produced according to the following equation: CS2 (l) + 3O2 (g) → CO2 (g) + 2SO2 (g) a. What is the percent yield of sulfur dioxide if the burning of 25.0g of carbon disulfide produces 40.5g of sulfur dioxide? ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ b. What is the percent yield of carbon dioxide if 2.5 mol of oxygen react and 32.4 g of 71 carbon dioxide are produced? ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ Powerful knowledge: Water of crystallisation Water of crystallisation or water of hydration are water molecules that are present inside crystals from their formation from aqueous solutions. The water molecules are held in the structure using dative bonds (covalent bonds where the water donates both pairs of electrons). Water of crystallisation can generally be removed by heating a sample until a constant mass (heating until the mass of the salt does not change). For example: CuSO4.5H2O → CuSO4 + 5H2O (Hydrated copper sulphate) (Anhydrous copper sulphate) (Water) 72 I do 1. 6.25g of blue hydrated copper (II) sulphate, CuSO4.xH2O, (x unknown) was gently heated in a crucible until the mass remaining was a constant 4.00g. Calculate the value of x. __________________________________________________________________________ ____________________________________________________________________
