ACSI 2022 HL Notes Stoichiometric Relationships (Teacher)

IBDP Chemistry HL/Stoichiometric Relationships Page 1 Anglo − Chinese School (Independent) Year 5 (2022) IBDP Chemistry HL (IB DP syllabus Topic 1) 1.1 Introduction to the particulate nature of matter and chemical change - Essential Idea: Physical and Chemical properties depends on the ways in which different atoms combine 1.2 The mole concept − Essential Idea: The mole make it possible to correlate the number of particles with the mass that can be measured. 1.3 Reacting masses and volumes − Essential Idea: Mole ratios in chemical equations can be used to calculate reacting ratios by mass and gas volume. (IB D P syllabus Topic 9) 9.1 Introduction to Oxidation and Reduction − Essential Idea: Redox reactions play a key role in many chemical and biochemical processes. TOPIC 1 STOICHIOMETRIC RELATIONSHIP S TEACHER COPY – WITH SUGGESTED SOLUTIONS

IBDP Chemistry HL/Stoichiometric Relationships Page 2 1.1 Introduction to the particulate nature of matter and chemical change Essential idea: Physical and chemical properties depend on the ways in which different atoms combine.  Nature of Science: • Making quantitative measurements with replicates to ensure reliability —definite and multiple proportions. Understandings: • Atoms of different elements combine in fixed ratios to form compounds, which have different properties from their component elements. • Mixtures contain more than one element and/or compound that are not chemically bonded together and so retain their individual properties. • Mixtures are either homogeneous or heterogeneous. Applications and skills: • Deduction of chemical equations when reactants and products are specified. • Application of the state symbols (s), (l), (g) and (aq) in equations. • Explanation of observable changes in physical properties and temperature during changes of state. Guidance: • Balancing of equations should include a variety of types of reactions. • Names of the changes of state— melting, freezing, vaporization (evaporation and boiling), condensation, sublimation and deposition—should be covered. • The term “latent heat” is not required. • Names and symbols of elements are in the data booklet in section 5. 1.2 The mole concept Essential idea: The mole makes it possible to correlate the number of particles with the mass that can be measured.  Nature of Science: • Concepts— the concept of the mole developed from the related concept of “equivalent mass” in the early 19th century. Understandings: • The mole is a fixed number of particles and refers to the amount, n, of substance. • Masses of atoms are compared on a scale relative to 12C and are expressed as relative atomic mass (Ar) and relative formula/molecular mass (Mr). • Molar mass (M) has the units g mol−1. • The empirical formula and molecular formula of a compound give the simplest ratio and the actual number of atoms present in a molecule respectively.

IBDP Chemistry HL/Stoichiometric Relationships Page 3 Applications and skills: • Calculation of the molar masses of atoms, ions, molecules and formula units. • Solution of problems involving the relationships between the number of particles, the amount of substance in moles and the mass in grams. • Interconversion of the percentage composition by mass and the empirical formula. • Determination of the m olecular formula of a compound from its empirical formula and molar mass. • Obtaining and using experimental data for deriving empirical formulas from reactions involving mass changes. Guidance: • The value of the Avogadro’s constant (L or NA) is given in the data booklet in section 2 and will be given for paper 1 questions. • The generally used unit of molar mass (g mol−1) is a derived SI unit. 1.3 Reacting masses and volumes Essential idea: Mole ratios in chemical equations can be used to calculate reacting ratios by mass and gas volume.  Nature of Science: • Making careful observations and obtaining evidence for scientific theories —Avogadro's initial hypothesis. Understandings: • Reactants can be either limiting or excess. • The experimental yield can be different from the theoretical yield. • Avogadro’s law enables the mole ratio of reacting gases to be determined from volumes of the gases. • The molar volume of an ideal gas is a constant at specified temperature and pressure. • The m olar concentration of a solution is determined by the amount of solute and the volume of solution. • A standard solution is one of known concentration. Applications and skills: • Solution of problems relating to reacting quantities, limiting and excess reactants, theoretical, experimental and percentage yields. • Calculation of reacting volumes of gases using Avogadro’s law. • Solution of problems and analysis of graphs involving the relationship between temperature, pressure and volume for a fixed mass of an ideal gas. • Solution of problems relating to the ideal gas equation. • Explanation of the deviation of real gases from ideal behaviour at low temperature and high pressure. • Obtaining and using experimental values to calculate the molar mass of a gas from the ideal gas equation. • Solution of problems involving molar concentration, amount of solute and volume of solution. • Use of the experimental method of titration to calculate the concentration of a solution by reference to a standard solution.

IBDP Chemistry HL/Stoichiometric Relationships Page 4 Guidance: • Values for the molar volume of an ideal gas are given in the data booklet in section 2. • The ideal gas equation, 𝑃𝑃V = 𝑛𝑛RT , and the value of the gas constant (R) are given in the data booklet in sections 1 and 2. • Units of concentration to include: g dm−3, mol dm−3 and parts per million (ppm). • The use of square brackets to denote molar concentration is required. 9.1 Introduction to redox and redox titration (IB Syllabus Topic 9) Essential idea: Redox (reduction–oxidation) reactions play a key role in many chemical and biochemical processes. Understandings: • Oxidation and reduction can be considered in terms of oxygen gain/hydrogen loss, electron transfer or change in oxidation number. • An oxidizing agent is reduced and a reducing agent is oxidized. Applications and skills: • Deduction of the oxidation states of an atom in an ion or a compound. • Identification of the species oxidized and reduced and the oxidizing and reducing agents, in redox reactions. • Deduction of redox reactions using half−equations in acidic or neutral solutions. • Solution of a range of redox titration problems. Guidance: • Oxidation number and oxidation state are often used interchangeably, though IUPAC does formally distinguish between the two terms. Oxidation numbers are represented by Roman numerals according to IUPAC. • Oxidation states should be represented with the sign given before the number, eg +2 not 2+. • The oxidation state of hydrogen in metal hydrides (−1) and oxygen in peroxides (−1) should be covered.

IBDP Chemistry HL/Stoichiometric Relationships Page 5 1.1 Introduction to the particulate nature of matter and chemical change Solids Liquids Gases • Particles are close together. • Particles have lower energy than in the other two states. • Particles can only rotate and vibrate about fixed positions. • Strong forces of attraction between particles. • Particles are slightly further apart than in solids. • Particles have larger amounts of energy than those in the solid state. • Particles can move about quite freely around one other while in close proximity. • Moderate forces of attraction between particles. (Some of the strong force