Quantitative Chemistry | AQA GCSE Chemistry, Higher tier (8462)

Quantitative Chemistry

152 questions
10 subtopics
Paper 1
Paper 1

Quantitative Chemistry is examined in Chemistry Paper 1.

It covers conservation of mass and balanced chemical equations, relative formula mass and concentration of solutions, mass changes when a gas is involved, and measurement uncertainty, moles, amounts of substances in equations, and balancing using moles, limiting reactants, percentage yield, atom economy, using concentrations of solutions in mol/dm and use of amount of substance in relation to volumes of gases.

Sample questions from Quantitative Chemistry

Answer each one closed book first, then open the answer.

Conservation of mass and balanced chemical equations

Explain why chemical reactions can be represented by balanced symbol equations.

Show the answer
Because no atoms are lost or made, the number of atoms of each element must be the same on both sides of the equation.
Relative formula mass and concentration of solutions

How is the percentage by mass of an element in a compound calculated?

Show the answer
Divide the total relative atomic mass of that element in the formula by the relative formula mass of the compound, then multiply by 100.
Mass changes when a gas is involved, and measurement uncertainty

What is always true about the result of any measurement that is made?

Show the answer
There is always some uncertainty in the value obtained.
Moles

How does the number of particles in one mole of one substance compare with the number in one mole of any other substance?

Show the answer
It is the same number of the stated particles in both.
Amounts of substances in equations, and balancing using moles

For Mg + 2HCl → MgCl₂ + H₂, how many moles of hydrochloric acid are needed to react completely with 0.5 mol of magnesium?

Show the answer
1 mol.
Limiting reactants

Which of two reactants decides the maximum amount of product that can form?

Show the answer
The limiting reactant, the one that runs out first.
Percentage yield

What is meant by saying that some reactants may react in ways different to the expected reaction?

Show the answer
They take part in side reactions that make other products, so less of the wanted product is formed.
Atom economy

What information is needed before the atom economy of a reaction can be calculated?

Show the answer
The balanced equation, and the relative formula masses of the desired product and of all the reactants.

The 10 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Conservation of mass and balanced chemical equations	The law of conservation of mass, calculating masses in sealed reactions, why reactions are shown by balanced equations, balancing the equations for hydrogen and methane burning, the difference between balancing numbers and subscripts, and counting atoms in formulae such as 3H₂SO₄ and 2Ca(OH)₂.	12
Relative formula mass and concentration of solutions	Defining and calculating relative formula mass, showing both sides of a balanced equation total the same, percentage by mass of an element, and concentration in g/dm³ from the mass of solute and the volume of solution.	16
Mass changes when a gas is involved, and measurement uncertainty	Why a metal gains mass when heated in air and a carbonate loses mass when decomposed, apparent breaches of conservation of mass explained with particles, the effect of sealing the container, uncertainty from the range of repeats, accuracy, precision, repeatability and reproducibility, random and systematic errors, anomalous results, resolution and reading scales, and mean, median and mode.	32
Moles	The mole as the unit of chemical amount, why it is used, the mass of one mole from relative formula mass, the Avogadro constant, and converting between mass and moles.	15
Amounts of substances in equations, and balancing using moles	The steps of a reacting mass calculation, mole ratios from balancing numbers, worked masses for magnesium oxide, carbon dioxide and ammonia, deducing a balanced equation from reacting masses, and rearranging the moles formula.	15
Limiting reactants	What the limiting reactant is, why one reactant is used in excess and what happens to it, which reactant fixes the mass of product, and worked examples with magnesium, oxygen, acid and ammonia.	11
Percentage yield	Why the theoretical mass of product is not always obtained, including reversible reactions, losses during separation and side reactions, yield and percentage yield, the percentage yield equation and why it cannot exceed 100%, worked percentage yield calculations, and calculating theoretical mass from a balanced equation.	13
Atom economy	What atom economy measures and why a high value matters for sustainability and cost, the information and equation needed to calculate it, why a single-product reaction scores 100%, worked calculations for calcium oxide, iron and zinc oxide, and weighing atom economy against yield, rate, equilibrium and by-products when choosing a pathway.	13
Using concentrations of solutions in mol/dm	Concentration in mol/dm³, calculating moles from concentration and volume, the mass of solute in a given volume, finding an unknown concentration from a titration, and what dilution does to concentration.	12
Use of amount of substance in relation to volumes of gases	Why equal moles of any gas fill the same volume, the 24 dm³ molar volume at room temperature and pressure, converting between mass, moles and volume, and volumes of reacting gases from an equation.	13

Quantitative Chemistry is 152 of the 1,648 questions in the guide.Get the guide, £7

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.