A-Level Chemistry (OCR): Free Mock Test & Practice Questions

A-Level Chemistry (OCR)

Physical, inorganic and organic chemistry. OCR board.

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Free practice questions

Try 3 real A-Level Chemistry (OCR) questions

Have a go, then reveal the worked explanation. A taster from a bank of 217 original questions — unlock for unlimited drills and full timed mocks.

Q1. Which type of bonding is present in solid magnesium oxide, MgO?

A. Simple molecular
B. Giant ionic
C. Giant covalent
D. Metallic

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✓ Answer: B. Giant ionic

MgO is formed by complete transfer of electrons from Mg to O, giving Mg2+ and O2- ions held together in a giant lattice by strong electrostatic attraction. This ionic bonding explains its very high melting point, unlike simple molecular substances such as CO2.

Q2. A student burns 0.65 g of ethanol (Mr = 46) under a copper calorimeter containing 100 g of water, raising the temperature by 22.0 °C. Using q = mcΔT with c = 4.18 J g⁻¹ K⁻¹, what is the experimental molar enthalpy of combustion?

A. −9.2 kJ mol⁻¹
B. −651 kJ mol⁻¹
C. −92 kJ mol⁻¹
D. −1367 kJ mol⁻¹

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✓ Answer: B. −651 kJ mol⁻¹

q = 100 × 4.18 × 22.0 = 9196 J = 9.196 kJ. Moles of ethanol = 0.65/46 = 0.01413 mol, so molar enthalpy = −9.196/0.01413 ≈ −651 kJ mol⁻¹. This is far less exothermic than the literature value (−1367 kJ mol⁻¹) because of heat loss to the surroundings in a simple calorimeter, a common source of experimental error.

Q3. How does increasing the concentration of the aqueous ions in a half-cell (away from standard 1 mol dm-3) generally affect the electrode potential, according to Le Chatelier-type reasoning used at A-level?

A. It has no effect on the electrode potential
B. Increasing the concentration of the oxidised species makes the electrode potential more negative
C. It always makes the electrode potential exactly zero
D. Increasing the concentration of the oxidised species (e.g. Mn+) makes the electrode potential more positive

Show answer & explanation

✓ Answer: D. Increasing the concentration of the oxidised species (e.g. Mn+) makes the electrode potential more positive

Increasing the concentration of the oxidised species shifts the equilibrium M^n+ + ne- ⇌ M further towards reduction, making the electrode more willing to be reduced, so its electrode potential becomes more positive than the standard value. Conversely, increasing the concentration of the reduced species makes the potential more negative.

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A-Level Chemistry (OCR) — common questions

Frequently asked

How many questions are in the A-Level Chemistry (OCR)?

The exam has 40 questions. Every Revision Robin mock uses the same 40-question format so your practice matches the real thing.

What is the pass mark for the A-Level Chemistry (OCR)?

You need 24 out of 40 correct to pass, which is about 60%. Our mocks mark you against this exact threshold.

How long do you get?

The test is timed at 60 minutes. Our full mock runs on the same clock so you can practise your pacing.

Are these the real exam questions?

No. Our questions are original and written to match the current syllabus, so they give realistic practice without copying the official paper. Every answer comes with a plain-English explanation. Always confirm current rules and content with OCR.