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3. Quantitative chemistry

Formula mass and conservation of mass

4 lessons
3.1 Conservation of mass Why mass is conserved in chemical reactions, how this links to balanced equations, and why the mass seems to change in open systems when a gas is given off or taken in. AQA Edexcel OCR 3.2 Relative formula mass and percentage by mass How to calculate the relative formula mass of a substance from relative atomic masses, including formulae with brackets, and how to calculate the percentage by mass of an element in a compound. AQA Edexcel OCR 3.3 Empirical formulae How to work out an empirical formula from reacting masses or percentage composition, how to find a molecular formula from the empirical formula and Mr, and the magnesium oxide experiment. Edexcel OCR 3.4 Measurements and uncertainty How to find the mean of repeat measurements, identify anomalous results, estimate uncertainty from the range, and understand resolution, accuracy and precision. AQA

Moles and reacting masses

4 lessons
3.5 The mole and Avogadro's constant What a mole is, the Avogadro constant, and how to convert between mass, moles and numbers of particles using Mr and 6.02 × 10^23. Higher only AQA Edexcel OCR 3.6 Reacting masses from equations How to use a balanced equation and relative formula masses to calculate the mass of a reactant or product, and how to work out the balanced equation from the masses that react. AQA Edexcel OCR 3.7 Limiting reactants What limiting reactants and reactants in excess are, how to identify the limiting reactant using moles, how it controls the mass of product, and how to use moles to balance equations. Higher only AQA Edexcel OCR 3.8 Concentration of solutions in g/dm³ What concentration means, how to calculate the concentration of a solution in g/dm3 from the mass of solute and volume, converting cm3 to dm3, and how changing the mass or volume changes the concentration. AQA Edexcel OCR

Yield, atom economy and more mole calculations

4 lessons
3.9 Percentage yield What the yield of a reaction is, how to calculate percentage yield and theoretical yield, and why the actual yield is almost always less than the theoretical yield. Separate only AQA Edexcel OCR 3.10 Atom economy What atom economy is, how to calculate it from a balanced equation, why a high atom economy is important for sustainable development, and how atom economy, yield, rate and other factors are used to choose a reaction pathway. Separate only AQA Edexcel OCR 3.11 Concentrations in mol/dm³ and titration calculations Calculating concentrations in mol/dm3, converting between mol/dm3 and g/dm3, and using titration results to calculate an unknown concentration or volume. Higher only Separate only AQA Edexcel OCR 3.12 Volumes of gases The volume of one mole of any gas at room temperature and pressure, how to calculate gas volumes from masses and equations, and how to use Avogadro's law to find the volumes of gases that react. Higher only Separate only AQA Edexcel OCR