Amount of Substance | AQA A-Level Chemistry (7405)
Amount of Substance
- 118 questions
- 8 subtopics
- Physical chemistry, drawn on by Paper 1 and Paper 2
- Paper 1, Paper 2 and Paper 3
Amount of substance is examined on Papers 1, 2 and 3, and is the topic every calculation in the specification leans on.
It runs from relative masses and the mole through gas volumes, formulae, yields and titrations.
Sample questions from Amount of Substance
Answer each one closed book first, then open the answer.
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Relative Atomic and Molecular Mass
How is relative molecular mass calculated from a molecular formula?
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By adding together the relative atomic masses of all atoms present in the molecular formula. -
The Mole and the Avogadro Constant
How is the number of moles of a substance calculated from its mass?
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Moles = mass ÷ Mᵣ -
The Ideal Gas Equation
What does T represent in the ideal gas equation?
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Temperature -
Empirical and Molecular Formula
What data can be used to calculate an empirical formula?
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Composition by mass or percentage composition by mass. -
Balanced Equations and Reaction Calculations
What is the final step in converting moles of product to mass of product?
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Multiply the moles of product by its molar mass -
Atom Economy and Percentage Yield
What is the definition of percentage yield?
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Percentage yield is the actual yield expressed as a percentage of the theoretical yield. -
Acid-Base Titrations: Principles, Indicators and Apparatus
What is the role of an indicator in an acid-base titration?
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To show when the end point has been reached by changing colour -
Acid-Base Titrations: Standard Solutions and Calculations
What is meant by concordant results in a titration?
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Results that are within 0.10 cm³ of each other
The 8 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Relative Atomic and Molecular Mass | What relative atomic and molecular mass mean, and why carbon-12 is the standard. | 13 |
| The Mole and the Avogadro Constant | The mole, the Avogadro constant, and converting between mass, moles and particles. | 12 |
| The Ideal Gas Equation | pV = nRT, the units each term must be in, and using it to find moles or molar mass. | 18 |
| Empirical and Molecular Formula | Working out empirical formula from composition, and scaling it to the molecular formula. | 10 |
| Balanced Equations and Reaction Calculations | Balancing equations and using the ratios in them to work out reacting masses. | 20 |
| Atom Economy and Percentage Yield | Calculating both, telling them apart, and why industry cares about each. | 15 |
| Acid-Base Titrations: Principles, Indicators and Apparatus | What a titration measures, choosing an indicator, and the apparatus and technique that make the result reliable. | 12 |
| Acid-Base Titrations: Standard Solutions and Calculations | Making up a standard solution, and working concentration out from titre using moles = concentration × volume. | 18 |
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.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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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.
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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.
Nearby topics
AQA A-Level Chemistry Active Recall Guide
Every topic, not just this one. 2,442 questions with their answers.