CET Sail: Chemistry 2023 PDF

E T CAIL! S with SCIENCE VOLUME 2: SCIENCE III. Chemistry CET sail with SCIENCE Topic Outline III. Chemistry 1. Unit conversion 2. Elements, compounds, and mixtures 3. States of Matter 4. Periodic Table 5. Electron Configuration 6. Chemical Reactions 7. Stoichiometry and Balancin...

E T CAIL! S with SCIENCE VOLUME 2: SCIENCE III. Chemistry CET sail with SCIENCE Topic Outline III. Chemistry 1. Unit conversion 2. Elements, compounds, and mixtures 3. States of Matter 4. Periodic Table 5. Electron Configuration 6. Chemical Reactions 7. Stoichiometry and Balancing Equations 8. Gas Laws E T CAIL! S 1 CET Sail: Chemistry 2023 I. UNIT CONVERSION International System of Units (SI) commonly known as the metric system the international standard for measurement made up of 7 base units that define the 22 derived units with special names and symbols SI Base Units Base Quantity Base Unit Name Typical Symbol Name Symbol time t second s length l, x, r, etc. meter m mass m kilogram kg electric current I, i ampere A thermodynamic T kelvin K temperature amount of substance n mole mol luminous intensity Iᵥ candela cd 2 CET Sail: Chemistry 2023 I. UNIT CONVERSION Image retrieved from nist.gov 3 CET Sail: Chemistry 2023 I. UNIT CONVERSION Conversion Factor a fraction in which the numerator and denominator are the same quantity expressed in different units this fraction is always equal to 1 may be multiplied to any given quantity without changing its value does not affect the number of significant figures of the quantity being multiplied to Example: 1 in = 2.54 cm may be written as a conversion factor in two ways: or This conversion factor may then be used in converting measurements of length from inches to centimeters or vice versa. (canceling the unit in from the numerator and denominator leaves us with cm) (the given quantity 10.00 in has 4 significant figures, so the final answer must also have 4 significant figures, i.e., 25.40 cm) 4 CET Sail: Chemistry 2023 I. UNIT CONVERSION Dimensional Analysis the use of conversion factors in problem solving allows for a systematic way of tracking units Example 1: An average adult has 5.2 L of blood. What is the volume of blood in cubic meters? Relevant conversions: 1 L = 1000 mL 1 mL = 1 cm³ 100 cm = 1 m³ Example 2: The density of silver is 10.5 g/cm³. What is its density in kg/m³? Relevant conversions: 1000 g = 1 kg 100 cm = 1 m 5 CET Sail: Chemistry 2023 II. ELEMENTS, COMPOUNDS, AND MIXTURES Classifications of Matter A. Pure Substance substances that contain only one type of particle and have a fixed constant structure due to constant composition, it also has a fixed boiling and melting points. Image retrieved from https://www.diffen.com/difference/Compound_vs_Mixture 6 CET Sail: Chemistry 2023 II. ELEMENTS, COMPOUNDS, AND MIXTURES Pure Elements 1. Element - a substance that consists of only one atom. it cannot be broken down or transformed into a new substance even by using some physical or chemical means. Elements are mostly metals, non- metals or metalloids. Ex. Gold, copper, silver, sodium 2. Compound - consists of two or more elements combined chemically in a fixed ratio. These substances can be broken down into separate elements by chemical methods. Ex. Table salt (NaCl), Glucose (C₆H₁₂O₆) B. Mixture consists of different kinds of elements and compounds combined physically and not chemically. Meaning, we can separate its components using simple means It does not have specific properties (e.g. boiling point and melting point). These properties ultimately depend on what component is dominant in the mixture. 7 CET Sail: Chemistry 2023 II. ELEMENTS, COMPOUNDS, AND MIXTURES 1. Heterogeneous Mixture - aka solution is comparatively unvarying in configuration or constant. For instance, when you prepare a glass of hot milk using powdered milk, the glass would contain a uniform mixture of water and milk, thus homogenous. No matter where you drink, the milk will taste the same since it would not be possible, under proper preparation, to have varying parts and taste of the milk (i.e. tasteless portion, very sweet portion, medium portion) 2. Homogeneous Mixture - is a concoction whose configuration varies from spot to spot within the sample. For example, if you put a little amount of sugar in a vessel, add some sand, and then shake the jar a couple of times, your concoction doesn’t have the same configuration all throughout the jar. As the sand is heftier, there’s possibly more amount of sand at the bottom of the jar and more sugar at the top part. These mixtures can be identified visually and separated easily by physical means. 8 CET Sail: Chemistry 2023 III. STATES OF MATTER Gas Liquid Solid Plasma assumes the assumes the shape and fixed volume shape of the part volume of its and shape of its container container rigid - particles particles can particles can locked into move/slide past move past one place Similar to a gas one another another Cloud of ionized particles not easily not easily Electrons compressible compressible compressible separated from lots of free space little free space little free space the nuclei between particles between between Found in flames, particles particles lightning, and does not flow auroras flows easily flows easily easily particles can particles can rigid - particles move past one move/slide past cannot another one another move/slide past one another Modified from https://www.chem.purdue.edu/gchelp/atoms/states.html 9 CET Sail: Chemistry 2023 III. STATES OF MATTER Phase Transitions Red: Higher temperature Blue: Lower temperature From: https://www.science-sparks.com/what-is-matter/ 10 CET Sail: Chemistry 2023 IV. PERIODIC TABLE Periodic Table: Basics Formulated by Dmitri Mendeleev Saw that elements, when arranged in increasing atomic weight, had repeating or periodic properties The elements found in one column of the periodic table share similar properties From: https://www.britannica.com/ 11 CET Sail: Chemistry 2023 IV. PERIODIC TABLE How to Read the Table The Table Period: One row Group: One column; Same number of valence electrons From: https://sciencenotes.org/periodic-table-groups-and-periods/ 12 CET Sail: Chemistry 2023 IV. PERIODIC TABLE One Element Atomic number: No. of protons in the nucleus Element symbol: One/two letters used to quickly identify the element Element name: The full name/identity of the element From: https://www.expii.com/t/how-to-read-the- Atomic weight: periodic-table-overview-components-8606 The average mass of one atom of the given element in atomic mass units (amu) Notable Elements or Types of Elements Hydrogen 1 proton, 1 electron Simplest element Gaseous and somewhat different from the elements below it Alkali Metals Group 1 (1st column) Soft metals Extremely reactive elements (can fizzle or explode in water) Usually found in nature as ionic compounds (e.g. Na in NaCl) 13 CET Sail: Chemistry 2023 IV. PERIODIC TABLE Notable Elements or Types of Elements Alkaline Earth Metals Group 2 (2nd column) Similar to Alkali Metals Soft, very reactive metals Transition Metals Big block in the middle of the table All are metals with varying properties (e.g. Iron, Copper, Gold, Titanium, etc.) Metalloids Diagonal line/staircase on the right side Have properties between metals and non-metals Mainly used in semiconductors and electronics (Silicon) Halogens 2nd to the last column Reactive and generally toxic/dangerous Chlorine, bromine, iodine, etc. Noble Gases Last column Complete electron shells Very Unreactive; rarely participate in reactions 14 CET Sail: Chemistry 2023 IV. PERIODIC TABLE From: https://sciencenotes.org/periodic-table-trends/ Periodic Trends Ionization Energy: Energy needed to remove an electron from the atom Electronegativity: Strength of attraction between electrons and the nucleus Atomic radius: General size of the atom Metallic/nonmetallic character: How “metallic” an element is (shiny, conductive, malleable, and ductile) 15 CET Sail: Chemistry 2023 IV. PERIODIC TABLE From: https://sciencenotes.org/electron-affinity-trend-and-definition/ Periodic Trends Electron Affinity: Energy released when an atom gains an additional electron/how readily an atom receives an electron GENERALLY follows electronegativity trend 16 CET Sail: Chemistry 2023 V. ELECTRON CONFIGURATION What is an Orbital? Shell? Subshell? Orbital It is a likely region where electrons would be found around a nucleus Has an associated energy level. It is like the potential energy between the negative electron and the positive nucleus Subshells Are made of multiple orbitals in the same energy level Shells Are made of subshells SHELLS contain SUBSHELLS which contain ORBITAL. Quantum Numbers There are 4 values that can describe the properties of an electron in an atom: n, l, mₗ, and mₛ From: https://byjus.com/chemistry/quantum-numbers/ 17 CET Sail: Chemistry 2023 V. ELECTRON CONFIGURATION 1. Principal Quantum Number (n) Designates principal electron shell of a specific electron Can be a positive integer 2. Angular Momentum Quantum Number/Azimuthal Quantum Number (l) Designates the shape of an electron subshell (s, p, d, or f) Subshells fall under an electron shell s: l = 0 p: l = 1 d: l = 2 f: l = 3 Can take any values from 0 to (n-1) 3. Magnetic Quantum Number (mₗ) Describes the orientation of a given orbital and the number of orbitals in one subshell E.g. a p orbital may be aligned along the x-axis, y-axis, or the z-axis. Therefore, there are 3 unique p orbitals For an orbital with a value l, ml takes a value from -l to l E.g. a p orbital with l = 1 can have mₗ of 1, 2, or 3 Note: Each shell has its own set of subshells and orbitals, so 2 shells can have 2 different sets of p orbitals. 18 CET Sail: Chemistry 2023 V. ELECTRON CONFIGURATION s, p, d, and f, Orbitals From: https://byjus.com/chemistry/quantum-numbers/ 19 CET Sail: Chemistry 2023 V. ELECTRON CONFIGURATION 4. Spin Quantum Number (mₛ) Gives the quantum spin of an electron Independent of the previous 3 values Either +½ or -½. Nothing else Rules 1. Aufbau Principle The “building up” rule Electrons fill the orbitals from lowest to highest energy s, p, d, and f are the subshells indicated with quantum number l 1, 2, 3, … are from the principal quantum number n, indicating the electron shell From: https://www.chemistrylearner.com/aufbau- principle.html 20 CET Sail: Chemistry 2023 V. ELECTRON CONFIGURATION 2. Hund’s Rule of Maximum Multiplicity When filling orbitals in the same energy level, one electron must fill all the orbitals BEFORE a second can fill it The electrons also must share the same spin (up or down) when From: https://www.chem.ucalgary.ca/courses filling the orbitals /351/mechanistic_etext/Ch01/ch1-2-2.html 3. Pauli Exclusion Principle In an atom, no electrons can share the same set of quantum numbers This means: i. Only two electrons can fill one orbital ii. One must be spin up and spin down (shown via arrows) From: https://www.chem.ucalgary.ca/courses /351/mechanistic_etext/Ch01/ch1-2-2.html 21 CET Sail: Chemistry 2023 V. ELECTRON CONFIGURATION Assigning Electron Configurations 1. Given an atom, find the number of electrons present. This is usually equal to the number of protons aka the atomic number on the periodic table. 2. Fill up the orbitals following the pattern below until you reach the correct no. of electrons. The big number is n, the shell The letters, s, p, d, and f are the subshells in a given shell The exponent/superscript shows the maximum number of electrons in the orbital I.e. 2p⁶ can hold up to 6 electrons. 4d¹⁰ can hold up to 10, and so on From: https://www.chem.fsu.edu/chemlab/chm1045/e_config.html 22 CET Sail: Chemistry 2023 V. ELECTRON CONFIGURATION 3. Noble Gas Notation: As a shortcut, a large part of the electron configuration can be shortened by using the electron configuration of a noble gas. Noble gases usually have full p orbitals Instead of writing down the full configuration, everything until np6 can be shortened into a noble gas form like [Ne] for 1s²2s²2p6 Example: Iodine Longer version: 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁵ Noble Gas notation: [Kr]5s²4d¹⁰5p⁵ [Kr] is a shorthand for the electron configuration from 1s² to 4p⁶ 4. Ions Add (anion) or remove (cation) an electron from the count when assigning electron configuration Example: Neutral Fluorine: 1s²2s²2p⁵ Fluorine anion: 1s²2s²2p⁶ 23 CET Sail: Chemistry 2023 VI. CHEMICAL REACTIONS Chemical Reaction - is an interaction between molecules in which the bonds are broken within reactant molecules, and new bonds are formed within product molecules in order to form a new substance. The rate of reaction depends on and is affected by factors like pressure, temperature, the concentration of reactants. Causes chemical change, i.e. color change, effervescence Chemical Equation - a nomenclature to express a chemical reaction: aA + bB → cC + dD A and B are the chemical formula of the reactants, while C and D are the chemical formula of the products. Coefficients (a, b, c, d) are usually seen in chemical equations to balance them out (see lesson 7) because chemical reactions follow the principle of law of conservation of mass (mass is neither created nor destroyed in chemical reactions, but is transformed). Meaning, the mass of the reactants is equal to the mass of the product. 24 CET Sail: Chemistry 2023 VI. CHEMICAL REACTIONS Types of Chemical Reactions Combustion Reaction - a combustible material (e.g. hydrocarbons) reacts with an oxidizer (e.g. O₂). Usually, a combustion reaction involves hydrocarbon and oxygen producing carbon dioxide and water. Note: Hydrocarbons are organic compounds consisting of hydrogen and carbon. CH₄ is a hydrocarbon. Decomposition Reaction - is a reaction in which a single component breaks down into multiple products. Example is the decomposition of table salt (NaCl) into its individual elements. Image retrieved from https://byjus.com/chemistry/chemical- reactions/#:~:text=A%20Chemical%20Reaction%20is%20a,formed%20compounds%2 0are%20called%20products. Synthesis Reaction - one of the most basic types of reaction wherein multiple simple compounds combine under certain physical conditions giving out a complex product. It is like the opposite of decomposition reaction. 25 CET Sail: Chemistry 2023 VI. CHEMICAL REACTIONS Types of Chemical Reactions Single-Displacement Reaction - is a reaction in which one element is substituted for another element in a compound. The starting materials are always a pure element and an aqueous compound. The general pattern of this reaction is: It can be seen that the pure element reactant replaces an element in the aqueous compound. Double-Displacement Reaction - another type of displacement reaction in which two aqueous reactants react and consequently, their anions and cations switch places forming two new products. An example is the reaction below: Image retrieved from https://byjus.com/chemistry/chemical- reactions/#:~:text=A%20Chemical%20Reaction%20is%20a,formed%20compounds%20are%20calle d%20products. 26 CET Sail: Chemistry 2023 VI. CHEMICAL REACTIONS Types of Chemical Reactions A double displacement reaction can be a neutralization reaction or a precipitation reaction: Neutralization Reaction - reaction between an acid and a base giving salt and water as the products. Precipitation Reaction - a reaction where an insoluble solid is formed. Image retrieved from https://www.google.com/url? sa=i&url=https%3A%2F%2Fslideplayer.com%2Fslide%2F14068081%2F&psig=AOvVaw12MVL9- Qt8hIVSB_3dCvEk&ust=1683768449756000&source=images&cd=vfe&ved=0CBEQjRxqFwoTCLDZ0Ou P6v4CFQAAAAAdAAAAABAD 27 CET Sail: Chemistry 2023 VI. CHEMICAL REACTIONS How to know if an insoluble salt/solid is formed in a precipitation reaction? There are actually rules in determining whether a product is aqueous (soluble in water/a compound that dissolves or dissociates in water) or insoluble (a compound that remains solid in the presence of water). This is called the Solubility Rules. Image retrieved from https://www.speedytemplate.com/solubility-rules-chart-1.png 28 CET Sail: Chemistry 2023 VI. CHEMICAL REACTIONS How to know if an insoluble salt/solid is formed in a precipitation reaction? There are actually rules in determining whether a product is aqueous (soluble in water/a compound that dissolves or dissociates in water) or insoluble (a compound that remains solid in the presence of water). This is called the Solubility Rules. Image retrieved from https://www.speedytemplate.com/solubility-rules-chart-1.png 29 CET Sail: Chemistry 2023 VII. STOICHIOMETRY & BALANCING CHEMICAL EQUATIONS NOTE: All figures in lesson VII were lifted from Burdge & Overby Chemical Equation a written representation of a chemical reaction or a physical process chemical species on the left side are reactants; right side, products the physical state of each reactant and product is specified in parentheses solid – (s) liquid – (l) gas – (g) aqueous (i.e., dissolved in water) – (aq) Law of Conservation of Mass basis of stoichiometry mass can neither be created nor destroyed another way of stating Dalton’s third hypothesis 30 CET Sail: Chemistry 2023 VII. STOICHIOMETRY & BALANCING CHEMICAL EQUATIONS John Dalton’s Atomic Theory Three Hypotheses Matter is composed of tiny, indivisible particles called atoms; all atoms of a given element are identical. Compounds are made up of specific combinations of atoms of two or more different elements. Chemical reactions cause the rearrangement of atoms, but do not cause either creation or destruction of atoms. Stoichiometry derived from ancient Greek words stoicheion (element) and metron (measure) refers to the use of numerical relationships between reactants and products in a chemical reaction to determine desired quantitative data Balancing Chemical Equations trial-and-error approach the goal is to have the same number of atoms on both sides of the equation, which may be done by raising their coefficients 31 CET Sail: Chemistry 2023 VII. STOICHIOMETRY & BALANCING CHEMICAL EQUATIONS General tips: 1. Change the coefficients of compounds (e.g., CO₂) before changing the coefficients of elements (e.g., O₂). 2. Treat polyatomic ions that appear on both sides of the equation (e.g., CO₃²⁻) as units, rather than counting their constituent atoms individually. 3. Count atoms and/or polyatomic ions carefully, and track their numbers each time you change a coefficient. 4. Ultimately, balancing equations takes a lot of patience and practice. Example: Balance the chemical equation for the combustion of butane: We first get the inventory of atoms on both sides: 32 CET Sail: Chemistry 2023 VII. STOICHIOMETRY & BALANCING CHEMICAL EQUATIONS We can balance C by placing a coefficient of 4 in front of CO₂, which changes the tally of atoms. Note that the coefficient 4 affects CO₂ as a whole (i.e., if CO₂ has 4 C atoms and 2 O atoms, then 4CO₂ have 4 C atoms and 8 O atoms. We can now balance H by placing a coefficient of 5 in front of H2O, resulting in 10 H atoms on both sides. Since there are 2 O atoms on the left side and 13 O atoms on the right side, we may place a coefficient of 13/2 in front of O₂ to balance. 33 CET Sail: Chemistry 2023 VII. STOICHIOMETRY & BALANCING CHEMICAL EQUATIONS Though this equation is already balanced, we may multiply everything by 2 so we get the smallest possible whole number coefficients: The molecules’ coefficients in a balanced chemical equation are also called stoichiometric coefficients. Calculations with Balanced Chemical Equations Mole the amount of substance that contains 6.022 x 10²³ of elementary particles (e.g., atoms, molecules, ions) Avogadro’s Number (N A) the number of atoms in exactly 12 grams of carbon-12, determined experimentally named in honor of Italian scientist Amadeo Avogadro (1776–1856) equal to 6.022 x 10²³ (i.e., has no unit) 34 CET Sail: Chemistry 2023 VII. STOICHIOMETRY & BALANCING CHEMICAL EQUATIONS Avogadro’s Constant equal to 6.022 x 10²³ particles/mol or 6.022 x 10²³ mol⁻¹ used to convert between moles and number of particles Molar Mass mass of one mole of a substance, expressed in g/mol used to convert between moles and grams the same as molecular mass and molecular weight (Note: mass and weight are used interchangeably in Chemistry) Interconverting Mass, Moles, and Number of Atoms Burdge & Overby 35 CET Sail: Chemistry 2023 VII. STOICHIOMETRY & BALANCING CHEMICAL EQUATIONS Mole Ratio relates the amounts in moles of any two substances in a balanced chemical equation may be used as a conversion factor when solving problems Example: From this balanced chemical equation We may obtain these mole ratios: Sample Problem (involving balancing, mole ratio, and interconversion): Given this reaction: How many grams of NaOH are required to fully consume 3.10 g of H₂SO₄? 36 CET Sail: Chemistry 2023 VII. STOICHIOMETRY & BALANCING CHEMICAL EQUATIONS Step 1: Balance the chemical equation. Balancing Na: Balancing O and H: 37 CET Sail: Chemistry 2023 VII. STOICHIOMETRY & BALANCING CHEMICAL EQUATIONS Step 2: Convert grams of H₂SO₄ to moles of H₂SO₄ using its molar mass. Step 3: Convert moles of H₂SO₄ to moles of NaOH using the mole ratio. Step 4: Convert moles of NaOH to grams of NaOH using its molar mass. (final answer is expressed in 3 s.f. since the given mass of H₂SO₄ in the problem is also 3 s.f.) 38 CET Sail: Chemistry 2023 VII. STOICHIOMETRY & BALANCING CHEMICAL EQUATIONS Limiting and Excess Reagent Limiting Reagent (LR) the reagent/reactant that is consumed completely in a chemical reaction the amount of this reactant limits the amount of product/s that can form determines the maximum amount of product/s formed Excess Reagent (ER) the reagent/reactant that is not consumed completely present in a quantity greater than necessary to completely react with limiting reagent Burdge & Overby Based on the kabobs analogy, mushrooms are the limiting “reagent” (LR) while the skewers and beef are the excess “reagents” (ER). 39 CET Sail: Chemistry 2023 VII. STOICHIOMETRY & BALANCING CHEMICAL EQUATIONS Reaction Yield Theoretical Yield the amount of product/s that will form if all the limiting reagent is consumed by the desired reaction Actual Yield the amount of product/s actually recovered determined experimentally % Yield a measure of the efficiency of a chemical reaction Sample Problem (involving limiting and excess reagents, % yield): 1. Determine what mass of NH₃ forms when 84.06 g N₂ and 22.18 g H₂ react according to the equation: N₂ + 3H₂ → 2NH₃ 2. Determine the percent yield if 99.9 g NH₃ was recovered at the end of the reaction. Step 1: Convert grams to moles using molar masses. 40 CET Sail: Chemistry 2023 VII. STOICHIOMETRY & BALANCING CHEMICAL EQUATIONS Step 2: Determine amount of NH3 formed from the two reactants. Since less NH3 is formed from N2, N2 is the limiting reagent (LR). Step 3: Convert moles of NH3 to grams using its molar mass. Step 4: Compute for the percent yield. 41 CET Sail: Chemistry 2023 VIII. GAS LAWS Boyle’s Law volume is inversely proportional to pressure Charles’s Law volume is directly proportional to temperature Avogadro’s Law volume is directly proportional to amount of substance Combined Gas Law Given these three gas laws: Problem Type Relates Requires Constant Boyle's Law P and V n and T Charles's Law T and V n and P Avogadro's Law n and V P and T we obtain the combined gas law: 42 CET Sail: Chemistry 2023 VIII. GAS LAWS Ideal Gas Equation Given the three gas laws/proportionalities, we obtain: where R is the proportionality constant, called Gas Constant. Rearranging, we obtain the ideal gas equation: Note that the units for P, V, and T will depend on the unit of the gas constant R. Various Equivalent Expressions of the Gas Constant, R Numerical Value Unit 0.08206 L atm/K mol 62.36 L torr/K mol 0.08314 L bar/K mol 8.314 m³ Pa/K mol 8.314 J/K mol 1.987 cal/K mol Note: the product of volume and pressure gives units of energy (joules, calories) 43 CET Sail: Chemistry 2023 VIII. GAS LAWS Relevant conversions for temperatures: CET Sail: Science, Chemistry. 2023 REFERENCES Burdge, J., & Overby, J. (2012) Chemistry: Atoms first. McGraw-Hill Higher Education. https://byjus.com/chemistry https://sciencenotes.org https://www.chem.purdue.edu/gchelp/atoms/states.html https://www.diffen.com/difference/Compound_vs_Mixture ttps://www.khanacademy.org https://www.livescience.com/28507-element-groups.html https://www.science-sparks.com/what-is-matter/ https://www.scienceworld About Us. CET Sail is a non-profit, student-run project intended to help senior high school students prepare for UPCAT 2024. Our target demographic is those especially who have difficulty in Math & Sciences and those who may not have immediate access to reviewers due to financial reasons, yet are avidly preparing for their examination. For contacts, you may message our Facebook Page Below: https://www.facebook.com/CETSail2023