AQA Chemistry Use of amount of substance in relation to masses of pure substances

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Moles (HT only)14 objectives

(HT only) State that chemical amounts are measured in moles.
(HT only) State that the symbol for the unit mole is mol.
(HT only) Explain that the mass of one mole of a substance in grams is numerically equal to its relative formula mass.
(HT only) Explain that one mole of a substance contains the same number of stated particles as one mole of any other substance.
(HT only) Define the Avogadro constant as the number of atoms, molecules or ions in one mole of a substance.
(HT only) Use the value 6.02 x 10^23 per mole for the Avogadro constant.
(HT only) Understand that amounts in moles can apply to atoms, molecules, ions, electrons, formulae and equations.
(HT only) Use relative formula mass to calculate the number of moles in a given mass of a substance.
(HT only) Use the number of moles and relative formula mass to calculate the mass of a substance.
(HT only) Rearrange the equation linking mass, relative formula mass and moles. (MS 3b)
(HT only) Recognise and use decimal form in mole calculations. (MS 1a)
(HT only) Recognise and use standard form when using Avogadro constant. (MS 1b)
(HT only) Use an appropriate number of significant figures in amount-of-substance calculations. (MS 2a)
(HT only) Use mathematical symbols such as =, <, >, proportionality and approximate relationships where appropriate. (MS 3a)

Amounts of substances in equations (HT only)9 objectives

(HT only) Interpret balanced chemical equations in terms of moles.
(HT only) Calculate masses of substances shown in a balanced symbol equation.
(HT only) Calculate masses of reactants from a balanced symbol equation and a given mass of another substance.
(HT only) Calculate masses of products from a balanced symbol equation and a given mass of a reactant or product.
(HT only) Use mole ratios from coefficients in balanced equations.
(HT only) Use ratios, fractions and percentages in reacting-mass calculations. (MS 1c)
(HT only) Substitute numerical values into algebraic equations using appropriate units. (MS 3c)
(HT only) Change the subject of equations used in reacting-mass calculations. (MS 3b)
(HT only) Recognise and use decimal form in mass calculations. (MS 1a)

Using moles to balance equations (HT only)7 objectives

(HT only) Convert given masses of reactants and products into amounts in moles.
(HT only) Convert numbers of moles into simple whole-number ratios.
(HT only) Use mole ratios calculated from masses to balance a symbol equation.
(HT only) Balance an equation given the masses of reactants and products.
(HT only) Change the subject of a mathematical equation when using mole calculations. (MS 3b)
(HT only) Substitute numerical values into equations using appropriate units. (MS 3c)
(HT only) Avoid confusing mole ratios with mass ratios when balancing equations from data.

Limiting reactants (HT only)7 objectives

(HT only) Define the limiting reactant as the reactant that is completely used up in a reaction.
(HT only) Explain why one reactant may be used in excess to ensure another reactant is completely used.
(HT only) Explain how a limiting quantity of reactant affects the amount of product possible.
(HT only) Explain limiting reactants in terms of amounts in moles.
(HT only) Explain limiting reactants in terms of masses in grams.
(HT only) Use balanced equations to identify which reactant limits product formation. (WS 4.1)
(HT only) Distinguish limiting-reactant explanations from percentage-yield explanations.

Concentration of solutions9 objectives

State that the concentration of a solution can be measured in mass per given volume of solution.
Use grams per cubic decimetre, g/dm^3, as a unit of concentration.
Calculate the mass of solute in a given volume of solution of known concentration.
Calculate concentration when given mass of solute and volume of solution.
Calculate volume when given mass of solute and concentration.
Use ratios, fractions and percentages in concentration calculations. (MS 1c)
Rearrange the equation linking concentration, mass and volume. (MS 3b)
(HT only) Explain how mass of solute and volume of solution are related to concentration.
Distinguish mass concentration in g/dm^3 from amount concentration in mol/dm^3.

MoleRelative Formula MassAvogadro constant

Understand Moles: Calculate carefully by always remember that chemical amounts are measured in moles (mol). This is fundamental for all calculations involving substances. Link your answer to Moles (HT only) in Use of amount of substance in relation to masses of pure substances, and show formula, substitution, calculation, final answer, and unit where relevant.
Remember the Unit Symbol: Calculate carefully by always use 'mol' as the symbol for the unit mole in your calculations. Link your answer to Moles (HT only) in Use of amount of substance in relation to masses of pure substances, and show formula, substitution, calculation, final answer, and unit where relevant.

Confusing moles with mass: Remember that moles measure the amount of substance, while mass is measured in grams. Use the relationship between mass and moles to clarify this distinction.
Confusing Mole Symbol: Remember that the correct symbol for the unit mole is 'mol', not 'M'. Keep the correction anchored to Moles (HT only); check formula, substitution, calculation, final answer, and unit where relevant.

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