Foundations in Chemistry PDF

2.1 - Atoms and reactions 2.1.1 - Atomic structure and isotopes The symbols for atomic no. and mass no. are... Z and A respectively. What is the Ar of a proton, 1, 1, and 1/1836 respectively. neutron, and electron? Define isotopes Atoms of same...

2.1 - Atoms and reactions 2.1.1 - Atomic structure and isotopes The symbols for atomic no. and mass no. are... Z and A respectively. What is the Ar of a proton, 1, 1, and 1/1836 respectively. neutron, and electron? Define isotopes Atoms of same element with the same number of protons but different numbers of neutrons. What do chemical properties Electronic structure. depend on? Thus isotopes have the same chemical properties. How do isotopes of the same In physical properties (e.g., density). element vary? Define both cation and anion Cation - positively charged ion. Anion - negatively charged ion. Remember as cats make you positive. Define relative isotopic mass The mass of an isotope compared to 1/12 of the mass of one carbon- 12 atom. Define relative atomic mass The weighted mean mass of one atom compared to 1/12 of the mass of one carbon-12 atom. What is the formula for the ∑(isotopic mass ⋅ relative abundance) Ar of a sample? total relative abundance What does a mass Mass to charge ratio (m/z). spectrometer measure? 2.1.2 & 2.1.3 - Compounds, formulae, equations, and amount of substance Formula of a zinc ion Zn2+ Formula of an ammonium NH4+ ion Formula of a silver ion Ag+ Formula of a nitrate ion NO3- Formula of a nitride ion N3- Formula of a carbonate ion CO32- Formula of a sulfate ion SO42- Formula of a phosphate ion PO43- What does a binary ONLY two different elements. compound contain? What is the mnemonic for Have No Fear Of Ice Cold Beer. remembering the diatomic H2, N2,, O2, I2, Cl2 Br2. elements? What are the steps for 1. Balance the equation. writing ionic equations? 2. Break each (aq) substance into ions. 3. Cancel any ions on both sides (these being the spectator ions). What are spectator ions? Ions that aren’t changing state or oxidation number. Define one mole The amount of substance which contains the same amount of particles as there are atoms in 12 grams of carbon-12. Define molar mass The mass in grams of 1 mol of a substance given in gmol-1. What is the equation linking 𝑚 mol (n), mass (m), and molar 𝑛= mass (Mr)? 𝑀𝑟 What is the equation linking volume of gas mol (n), volume of gas (dm3), 𝑛= and molar gas volume (24 molar gas volume dm3)? This is used for anything under standard conditions. Define molecular formula The ACTUAL number of atoms of EACH ELEMENT in an element/compound. Define empirical formula The SIMPLEST ratio of atoms of EACH ELEMENT in an element/compound. In what contexts is 'relative Relative molecular mass - used for easily defined structures molecular mass' and 'relative in which you know the exact no. of atoms (e.g., O2). formula mass' used? Relative formula mass - used for giant structures in which you don’t know the exact no. of atoms (e.g., lattices such as NaCl). What is a hydrated/hydrous A salt molecule loosely attached to water (called waters of salt? crystallization). Thus anhydrous means the opposite. What is a solute? What is being dissolved into the solvent. What is a solvent? The liquid in which a solute is dissolved in to form a solution. What is 1 L equal to (in 1dm3. volume)? What is the ideal gas equation and what is each 𝑝𝑉 = 𝑛𝑅𝑇 Where p is pressure (Pa), V is volume (m3), n is moles (mol), R is the unit measured in? gas constant, T is temperature (K). What is the conversion factor Add 273 to C to get K. between Kelvin and Celsius? What is a limiting reagent? A reactant that runs out first and thus limits how much product can be formed. Give 2 reasons for the Reaction may have not had enough time to go to completion. percentage yield being less A side reaction has taken place (e.g., in the glassware). than 100% Product was lost under purification. What is a salt? The product of a neutralisation reaction where the H+ IONS from the acid is replaced by metal or ammonium IONS. 2.1.4 & 2.1.5 - Acids and redox What are standard A solution for which its concentration is known accurately. solutions? What 3 things should you 1. Ensure you have clean dry equipment. ensure when making 2. Make washings to remove any salt BEFORE MAKING up the standard solutions? solution to the specified amount. 3. Invert the volumetric flask to ensure everything is dissolved. How does ammonia react ammonia + acid → ammonium salt with acid? 𝑁𝐻3 (𝑎𝑞) + 𝐻𝑁𝑂3 (𝑎𝑞) → 𝑁𝐻4 𝑁𝑂3 (𝑎𝑞) Give 3 strong acids and 1 Strong acids include: HCl, H2SO4, and HNO3. weak acid Weak acids include carboxylic acids such as CH3COOH. Give 1 weak base NH3 What are diprotic and Diprotic acids and triprotic acids donate two and three triprotic acids (with protons respectively. examples) and what does Examples include: H2SO4 and H3PO4. this mean for neutralisation? They need 2x or 3x the number of moles of base to be neutralised. Give 4 bases/types of bases Metal oxides, metal hydroxides, metal carbonates, and ammonia. What are bases and alkalis? Bases are H+ ion acceptors. Alkalis are soluble bases that release HO- ions into solution. Reaction between an acid acid + metal oxide → a salt + water and metal oxide Reaction between an acid acid + metal carbonate → a salt + water + carbon dioxide and metal carbonate Reaction between an acid acid + metal → salt + hydrogen and metall (+ type of reaction) redox (not neutralisation as water isn't formed) Reaction between an acid acid + metal hydroxide → a salt + water and metal hydroxide What is atom economy and A measure of how efficient a reaction is. how is it calculated? Mr of design products atom economy = Mr of reactants What are the 2 types of Addition - the reactants form a single DESIRED product reactions under atom (100%). economy? Substitution - the atoms from a reactant are substituted by others leading to more than one product. Addition reactions are usually where a reactant is added to an unsaturated molecule to make saturated molecule. Give 3 reasons for why a high Environmental friendly (due to less waste). atom economy is good Economical (due to not separating materials). Sustainable (as it prolongs finite materials). Give 2 ways of improving 1. Use an alternate reaction pathway with a higher atom atom economy economy. 2. Find a use for the waste products. What is oxidation number? The no. of electrons removed from an atom. What are the 4 main rules for 1. Elements always have an oxidation no. of 0. oxidation numbers? 2. Sum of oxidation no.’s in a compound = 0. 3. Sum of oxidation no.’s of an ion = its charge. 4. The most electronegative element in a compound is always negative (so work with this first). What are the 3 exceptions to 1. Hydrogen is always +1 except when in a hydride where it’s -1. oxidation rules? 2. Oxygen is always -2 except with fluorine (more electronegative) and as peroxides where it’s -1.  3. Chlorine is always -1 except when bonded with oxygen and fluorine (more electronegative) where it’s different. What is a hydride? A binary compound of hydrogen and a metal. What is a peroxide? A compound containing two oxygen atoms bonded together (O-O). What is an -ide? A binary compound in which the nonmetal is given an -ide suffix (e.g., sodium oxide). What are oxidising and Oxidising agents gain electrons leading to oxidation reducing agents? elsewhere. Reducing agents lose electrons leading to reduction elsewhere. What is a reduction reaction? Reduction reactions are the loss of oxygen atoms or gaining What is a oxidation reaction? of electrons. Opposite for oxidation. What do -ate compounds Oxygen and at least one other element. contain? Examples include: chlorate, nitrate, and carbonate. What is the end point in a The point where the indicator changes colour. titration? 2.2 - Electrons, bonding and structure 2.2.1 - Electron structure What do most noble gases ns2np6. have an outermost electron structure of? Which shells have which 1 has s. subshells? 2 has s p. 3 has s p d. 4 has s p d f. What are orbitals? Regions around the nucleus that can hold 2 electrons with opposite spins. What are degenerate Orbitals that have the same energy levels. orbitals? Eg, p-subshell consists of 3 degenerate p-orbitals. How many orbitals does each s has 1 orbital. subshell have? p has 3 orbitals. d has 5 orbitals. f has 7 orbitals. How do atoms fill up with In subshells, in order of increasing energy. electrons? What is the shape of an s- Sphere. orbital/s-subshell? The greater the shell number, the greater the radius. What are the shapes of the Dumbbells. p-orbitals? What are the 2 rules for all 1. Electrons won't pair in the same subshell if they don't have orbitals of the same energy? to. 2. Electrons in the same orbitals must have opposite spin. This is to avoid repulsion. Which key orbital fills first The s-orbital, past and including the 4th shell. and empties first, when, and It has less energy than the d-orbital but when the d-orbital why? gains electrons, it drops below s-orbital. What are the blocks of the periodic table? 2.2.2 - Bonding and structure What is a σ-bond? The overlap of orbitals directly between atoms. Define ionic bond The electrostatic force of attraction between oppositely charged ions formed by electron transfer. Describe and explain the Doesn't conduct when solid (1) because the ions are fixed in a conductivity of ionic lattice (1) so cannot carry a charge. compounds under different Conducts when molten or dissolved because the ions can states move and thus act as charge carriers (2). Why are ionic compounds As water molecules are polar solvents (1) so will surround each ion soluble? (1). Why are some ionic Greater charge difference (e.g., Mg2+ and O2-) meaning stronger compounds less soluble than attraction which is less easily overcome. others? Define covalent bond The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms. Give an example of a BF3. covalent molecule whose central atom has fewer than 8 electrons in its outermost shell What must an atom have Its d subshell meaning the atom must have 3 or more shells. access to for expansion of the octet to occur? You can only hold 8 electrons in an sp hybrid so require the d subshell to hold more. Give an example of a PF5. molecule which expands the octet Trigonal bipyramidal. How is PF5 formed (electron- By freeing up 5 orbitals by moving electrons into unoccupied d wise)? subshell orbitals. This is an spd hybrid that can hold more than 8 unlike the sp hybrid. What is a coordinate/dative A shared pair of electrons where both electrons are from the same bond? atom. What is used to show a An arrow from the atom providing the coordinate bond. E.g., in an coordinate bond? ammonium ion. Give the 3 bond angles 1. The bond angle between lone pairs. largest to smallest 2. The bond angle between a lone pair and a bonding pair. 3. The bond angle between bonding pairs. What are the 3 wedges for 1. Solid line is a bond on the plane of the page. shape of molecules? 2. Solid wedge is a bond that comes out of the plane of the page. 3. Dotted line is a bond going into the plane of the page. What do lone pairs repel by An extra 2.5° as they’re closer to the nucleus and thus take up more and why? space. Describe the linear shape of 2 bonding pairs. molecule with an example 180 degrees.  An example is CO2. Describe the trigonal planar Planar meaning flat on the page shape of molecule with an 3 bonding pairs and 0 lone pairs. example 120 degrees. An example is BF3. Describe the tetrahedral 4 bonding pairs. shape of molecule with an 109.5 degrees. example An example is NH4. Describe the pyramidal 3 bonding pairs and 1 lone pair. shape of molecule 107 degrees (because tetrahedral minus 2.5 degrees). Describe the nonlinear shape 2 bonding pairs and 2 lone pairs. of molecule 104.5 degrees between bonding pairs (because tetrahedral minus 2 x 2.5 degrees). The angle between the two lone pairs is the greatest. Describe the octahedral 6 bonding pairs. shape of molecule with an 90 degrees. example An example is SF6 How should you tackle a 1. State the no. of BONDING PAIRS and lone pairs ‘surrounding ‘explain the shape of the central atom‘. molecule’ question in 4 2. State that ‘electrons repel and try to get as far apart as steps? possible’ (1). 3. If there are lone pairs, state lone pairs repel more than BONDING PAIRS (1). Otherwise state electron pairs get repelled equally (1). 4. State the shape of molecule with the bond angle. Treat double bonds as single bonds here. Why are chemists able to As electron pairs REPEL (1) and the shape is determined by the no. of predict the shapes of bonding pairs and the no. of lone pairs (1). molecules? Define electronegativity The ability of an atom to attract electrons (1) in a covalent bond (1) towards itself. When can you tell a bond is Generally, if the two atoms are of different elements, it’s polar polar? (except for carbon-hydrogen). How can a molecule be As it’s symmetrical (1) so dipoles cancel each other out (1). nonpolar yet contain polar bonds? How can you work out if a Generally, if it has no lone pairs and the same bond pairs then it’s molecule is symmetrical? symmetrical. You may have to rotate it in different planes to confirm this. What are permanent dipole- Electrostatic forces of attraction between polar molecules dipole interactions? Which will have a higher HF ∵ stronger permanent dipole-dipole interactions (due to the b.p., HF or HCl, and why? difference in electronegativity being greater) which requires more energy to overcome. What are ‘London Forces’ Induced-dipole-dipole interactions. also called? Calling them ‘Van der Waals’ is too ambiguous. Does every structure have No. Lattices like SiO2. London Forces? If so which ones don't? Describe induced dipole- Unequal distribution of electrons (1) ⇒ temporary/instantaneous dipole interactions dipole (1) ⇒ induces a dipole in a nearby molecule (1) leading to attraction. Why do the strength of The no. of electrons increases ⇒ stronger dipoles (due to stronger induced dipole-dipole charges) ⇒ stronger attraction. interactions increase down groups? This is why oxygen has a higher b.p. than hydrogen. What is a hydrogen bond? The electrostatic attraction between a hydrogen atom bonded to an electronegative atom and a lone pair on an electronegative atom of a different molecule. The bond is represented by a dashed line and the line must be parallel to the covalent bond from the hydrogen. Which electronegative Oxygen, nitrogen, and fluorine ∵ they’re the most electronegative elements will hydrogen and most dense in electrons. bonding happen with and why? Chlorine’s electron density is too low due to its extra shell. Give 3 reasons why water 1. Hydrogen bonding provide it with stronger intermolecular has a higher m.p. and b.p. to forces. structurally similar 2. Forms up to four hydrogen bonds. compounds 3. Oxygen is the second most electronegative meaning stronger hydrogen bonds. Describe and explain the 2 1. Ice is less dense than water as the molecules are held apart anomalous properties of ice by hydrogen bonds in an open lattice. 2. Ice has a higher m.p. than expected as hydrogen bonds provides it with strong intermolecular forces. What causes high surface Hydrogen bonding leading to a strong and flexible lattice structure. tension in water and why? What can polar molecules Polar solvents and nonpolar solvents respectively. and nonpolar molecules dissolve into? This means nonpolar molecules (e.g., oil) are insoluble in water. Why doesn’t water and oil Water is polar and oil is nonpolar and the strongest bonds oil can mix? make is with other oil molecules and this is the same for water. This need for stability leads to separation. What are the strongest to 1. Hydrogen bonds the weakest intermolecular 2. Permanent dipole-dipole interactions. forces? 3. Induced dipole-dipole interactions. Yet, London forces can become stronger than the other 2 if there are a lot of electrons. Why is a p-block element As its highest energy electron occupies a p-orbital. considered a p-block element? This is because the water molecules are slightly attracted to the polar areas of a CO2 molecule. Why won’t all CO2 be As CO2 is slightly soluble. released from a reaction involving a solution? How does the structure of 1. Na, Mg, Al - giant metallic lattices. elements change across 2. S - giant covalent lattice. period 3? 3. P4, S8, Cl2, Ar - simple molecular.