Acids and Bases | AQA A-Level Chemistry (7405)
Acids and Bases
- 117 questions
- 7 subtopics
- Physical chemistry, drawn on by Paper 1 and Paper 2
- Paper 1, Paper 2 and Paper 3
Acids and bases is examined on Papers 1 and 3, and is the most calculation-heavy topic in physical chemistry.
It runs from the Brønsted-Lowry definition through pH of strong and weak acids and bases to titration curves, indicators and buffers.
Sample questions from Acids and Bases
Answer each one closed book first, then open the answer.
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Brønsted-Lowry Acid-Base Equilibria
What is a conjugate acid?
Show the answer
The species formed when a base accepts a proton -
Brønsted-Lowry Acid-Base Equilibria
Explain why water is described as amphoteric in the Brønsted-Lowry sense.
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Water can donate a proton to act as an acid, forming OH⁻, or accept a proton to act as a base, forming H₃O⁺ -
The pH Scale and Strong Acids
What is a strong acid?
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An acid that completely dissociates in aqueous solution -
The pH Scale and Strong Acids
What is the hydrogen ion concentration of a solution with pH 2.5?
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[H⁺] = 10⁻²·⁵ = 3.16 × 10⁻³ mol dm⁻³ -
The Ionic Product of Water and Strong Bases
Why are the concentrations of H⁺ and OH⁻ equal in pure water?
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Water dissociates to produce equal numbers of H⁺ and OH⁻ ions. -
The Ionic Product of Water and Strong Bases
How do you calculate [OH⁻] for a solution of a strong base like NaOH?
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[OH⁻] equals the concentration of the strong base (for monobasic bases like NaOH). -
Weak Acids and Ka
What does a larger Ka value indicate about acid strength?
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The acid is stronger and dissociates to a greater extent -
Weak Acids and Ka
How is the concentration of H⁺ ions related to the concentration of A⁻ ions for a weak acid in water?
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They are equal, since each molecule of HA that dissociates produces one H⁺ ion and one A⁻ ion
The 7 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Brønsted-Lowry Acid-Base Equilibria | Acids as proton donors and bases as proton acceptors, and identifying conjugate pairs in an equilibrium. | 16 |
| The pH Scale and Strong Acids | pH as a logarithmic scale, and calculating pH of a strong acid and back again. | 12 |
| The Ionic Product of Water and Strong Bases | Kw, its value at 25°C, and using it to find the pH of a strong base. | 20 |
| Weak Acids and Ka | Partial dissociation, the Ka and pKa expressions, and calculating the pH of a weak acid. | 17 |
| pH Curves and Acid-Base Titrations | The four curve shapes, locating the equivalence point, and reading pKa from the half-neutralisation point. | 28 |
| Indicators | How an indicator works, and choosing one whose range falls on the vertical section of the curve. | 8 |
| Buffer Solutions | What buffers are made from, how they resist pH change, and calculating the pH of one. | 16 |
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.