IB Chemistry SL Paper 1A Multiple-Choice Practice Paper (2025 syllabus)

Level: Year 10–11 (IB) | Subject: Chemistry SL | Time: 49 minutes | Total: 30 marks | Parts: 30

Paper at a glance

Paper	Time	Marks	Weighting
Paper 6 (Alternative to Practical)	1 h	40	20%

Questions

Question 1 (1 marks) — Amount of substance

(a) What amount, in mol, is 4.4 g of carbon dioxide (Mr = 44)?　A 0.20　B 0.44　C 0.05　D 0.10 (1 marks)

Question 2 (1 marks) — Amount of substance

(a) 0.25 mol of solute is dissolved and made up to 500 cm³. What is the concentration in mol dm⁻³?　A 2.00　B 0.125　C 0.25　D 0.50 (1 marks)

Question 3 (1 marks) — Amount of substance

(a) At STP the molar volume is 24 dm³ mol⁻¹. What volume is occupied by 0.15 mol of gas?　A 4.8 dm³　B 1.6 dm³　C 2.4 dm³　D 3.6 dm³ (1 marks)

Question 4 (1 marks) — Amount of substance

(a) A reaction has a theoretical yield of 8.0 g and an actual yield of 6.4 g. What is the percentage yield?　A 125.0%　B 62.5%　C 75.0%　D 80.0% (1 marks)

Question 5 (1 marks) — Amount of substance

(a) How many particles are in 0.50 mol (L = 6.02 × 10²³ mol⁻¹)?　A 3.0 × 10²³　B 6.0 × 10²³　C 1.2 × 10²⁴　D 3.0 × 10²² (1 marks)

Question 6 (1 marks) — Acids and bases

(a) A solution has [H⁺] = 1.0 × 10⁻³ mol dm⁻³. What is its pH?　A 3.00　B 11.00　C 14.00　D 1.00 (1 marks)

Question 7 (1 marks) — Atomic structure and periodicity

(a) What is the relative molecular mass of Mg(NO₃)₂ (Mg = 24.3, N = 14.0, O = 16.0)?　A 148　B 172　C 86　D 124 (1 marks)

Question 8 (1 marks) — Amount of substance

(a) What is the mass of 0.20 mol of sodium hydroxide (Mr = 40.0)?　A 2.0 g　B 4.0 g　C 8.0 g　D 20.0 g (1 marks)

Question 9 (1 marks) — Amount of substance

(a) 2H₂(g) + O₂(g) → 2H₂O(l). 4.0 mol of hydrogen reacts with 3.0 mol of oxygen. What is the maximum amount of water formed?　A 2.0 mol　B 3.0 mol　C 4.0 mol　D 6.0 mol (1 marks)

Question 10 (1 marks) — Amount of substance

(a) 25.0 cm³ of 0.400 mol dm⁻³ solution is diluted to 100.0 cm³. What is the new concentration?　A 0.100 mol dm⁻³　B 0.200 mol dm⁻³　C 0.400 mol dm⁻³　D 0.040 mol dm⁻³ (1 marks)

Question 11 (1 marks) — Amount of substance

(a) A titration uses a mean volume of 24.60 cm³ of 0.100 mol dm⁻³ solution. What amount of solute was used?　A 1.00 × 10⁻³ mol　B 2.46 × 10⁻² mol　C 2.46 × 10⁻³ mol　D 4.06 × 10⁻³ mol (1 marks)

Question 12 (1 marks) — Energetics

(a) 100.0 g of water rises in temperature by 6.5 °C. What energy is absorbed (c = 4.18 J g⁻¹ °C⁻¹)?　A 2.7 kJ　B 6.5 kJ　C 27.2 kJ　D 0.65 kJ (1 marks)

Question 13 (1 marks) — Energetics

(a) If that energy came from 0.0500 mol of reactant, what is the molar enthalpy change ΔH?　A −5.4 kJ mol⁻¹　B −27.2 kJ mol⁻¹　C −54.3 kJ mol⁻¹　D −108.7 kJ mol⁻¹ (1 marks)

Question 14 (1 marks) — Kinetics

(a) Gas volume rises from 12.0 cm³ at 20 s to 36.0 cm³ at 60 s. What is the average rate?　A 0.30 cm³ s⁻¹　B 0.40 cm³ s⁻¹　C 0.60 cm³ s⁻¹　D 1.20 cm³ s⁻¹ (1 marks)

Question 15 (1 marks) — Equilibrium

(a) At equilibrium for A + B ⇌ C, [A] = 0.20, [B] = 0.10 and [C] = 0.40 mol dm⁻³. What is Kc?　A 0.50　B 2.00　C 5.00　D 20.0 (1 marks)

Question 16 (1 marks) — Redox and electrochemistry

(a) What is the oxidation number of chromium in Cr₂O₇²⁻?　A +3　B +5　C +6　D +7 (1 marks)

Question 17 (1 marks) — Atomic structure and periodicity

(a) Which electron arrangement (by shell) is correct for iron (Z = 26)?　A 2,8,14,2　B 2,8,15,1　C 2,8,16,0　D 2,8,8,8 (1 marks)

Question 18 (1 marks) — Amount of substance

(a) 0.10 mol of Al₂(SO₄)₃ dissolves completely. What is the total amount of ions in solution?　A 0.10 mol　B 0.20 mol　C 0.30 mol　D 0.50 mol (1 marks)

Question 19 (1 marks) — Amount of substance

(a) What is the percentage by mass of oxygen in calcium carbonate, CaCO₃ (Mr = 100.1)?　A 12.0%　B 40.0%　C 48.0%　D 60.0% (1 marks)

Question 20 (1 marks) — Amount of substance

(a) A compound contains 40.0% C, 6.7% H and 53.3% O by mass. What is its empirical formula?　A CH₂O　B C₂H₄O　C C₂H₆O　D CHO (1 marks)

Question 21 (1 marks) — Amount of substance

(a) What amount of gas occupies 2.00 × 10⁻³ m³ at 1.00 × 10⁵ Pa and 300 K (R = 8.314 J K⁻¹ mol⁻¹)?　A 0.040 mol　B 0.080 mol　C 0.80 mol　D 8.02 mol (1 marks)

Question 22 (1 marks) — Amount of substance

(a) A gas has a density of 1.96 g dm⁻³ at STP. What is its molar mass?　A 24.0　B 47.0　C 58.0　D 94.0 (1 marks)

Question 23 (1 marks) — Redox and electrochemistry

(a) A current of 2.00 A passes through copper(II) sulfate for 1800 s. What mass of copper is deposited (F = 96 500 C mol⁻¹, Cu = 63.5)?　A 0.59 g　B 1.18 g　C 2.37 g　D 3.55 g (1 marks)

Question 24 (1 marks) — Experimental data processing

(a) A burette accurate to ±0.05 cm³ measures 25.00 cm³. What is the percentage uncertainty?　A 0.05%　B 0.20%　C 0.50%　D 2.00% (1 marks)

Question 25 (1 marks) — Energetics

(a) In A + B → C the desired product C has Mr 88, while A and B have Mr 20 and 24. What is the atom economy?　A 33.3%　B 50.0%　C 66.7%　D 88.0% (1 marks)

Question 26 (1 marks) — Amount of substance

(a) N₂ + 3H₂ → 2NH₃. 3.0 mol of nitrogen reacts completely with 9.0 mol of hydrogen. What amount of ammonia forms?　A 3.0 mol　B 6.0 mol　C 9.0 mol　D 12.0 mol (1 marks)

Question 27 (1 marks) — Energetics

(a) 2H₂ + O₂ → 2H₂O. Bond enthalpies: H–H 436, O=O 498, O–H 464 kJ mol⁻¹. What is ΔH?　A −486 kJ mol⁻¹　B −186 kJ mol⁻¹　C +486 kJ mol⁻¹　D +1370 kJ mol⁻¹ (1 marks)

Question 28 (1 marks) — Amount of substance

(a) 0.30 g of a gas occupies 0.24 dm³ at STP. What is its molar mass?　A 15.0　B 30.0　C 45.0　D 60.0 (1 marks)

Question 29 (1 marks) — Amount of substance

(a) 50 cm³ of 0.20 mol dm⁻³ solution is mixed with 50 cm³ of 0.60 mol dm⁻³ of the same solute. What is the final concentration?　A 0.20 mol dm⁻³　B 0.40 mol dm⁻³　C 0.60 mol dm⁻³　D 0.80 mol dm⁻³ (1 marks)

Question 30 (1 marks) — Kinetics

(a) A reactant halves in concentration every 20 s. What percentage remains after 80 s?　A 3.13%　B 6.25%　C 12.5%　D 25.0% (1 marks)

Answers and marking notes

Question 1 — Amount of substance

(a) D: n = m / Mr = 4.4 / 44.0 = 0.10 mol. [1 marks]

Question 2 — Amount of substance

(a) D: c = n / V = 0.25 / 0.500 = 0.50 mol dm⁻³ (500 cm³ = 0.500 dm³). [1 marks]

Question 3 — Amount of substance

(a) D: V = n × 24 = 0.15 × 24 = 3.6 dm³. [1 marks]

Question 4 — Amount of substance

(a) D: Yield = 6.4 / 8.0 × 100% = 80.0%. [1 marks]

Question 5 — Amount of substance

(a) A: N = 0.50 × 6.02 × 10²³ = 3.01 × 10²³, i.e. 3.0 × 10²³ to 2 s.f. [1 marks]

Question 6 — Acids and bases

(a) A: pH = −log₁₀[H⁺] = −log₁₀(1.0 × 10⁻³) = 3.00. [1 marks]

Question 7 — Atomic structure and periodicity

(a) A: Mr = 24.3 + 2 × (14.0 + 3 × 16.0) = 24.3 + 124.0 = 148.3 ≈ 148. [1 marks]

Question 8 — Amount of substance

(a) C: m = n × Mr = 0.20 × 40.0 = 8.0 g. [1 marks]

Question 9 — Amount of substance

(a) C: Hydrogen needs only 2.0 mol of O₂ (4.0 / 2), so H₂ is limiting; n(H₂O) = n(H₂) = 4.0 mol. [1 marks]

Question 10 — Amount of substance

(a) A: n is unchanged: c₁V₁ = c₂V₂ → 0.400 × 25.0 = c₂ × 100.0, c₂ = 0.100 mol dm⁻³. [1 marks]

Question 11 — Amount of substance

(a) C: n = c × V = 0.100 × 24.60 / 1000 = 2.46 × 10⁻³ mol. [1 marks]

Question 12 — Energetics

(a) A: q = mcΔT = 100.0 × 4.18 × 6.5 = 2 717 J = 2.7 kJ. [1 marks]

Question 13 — Energetics

(a) C: ΔH = −q / n = −2.717 / 0.0500 = −54.3 kJ mol⁻¹ (exothermic, hence negative). [1 marks]

Question 14 — Kinetics

(a) C: Rate = ΔV / Δt = (36.0 − 12.0) / (60 − 20) = 0.60 cm³ s⁻¹. [1 marks]

Question 15 — Equilibrium

(a) D: Kc = [C] / ([A][B]) = 0.40 / (0.20 × 0.10) = 20.0. [1 marks]

Question 16 — Redox and electrochemistry

(a) C: 2x + 7(−2) = −2 → 2x = +12 → x = +6. [1 marks]

Question 17 — Atomic structure and periodicity

(a) A: 1s²2s²2p⁶3s²3p⁶3d⁶4s², i.e. 2, 8, 14, 2 by shell; the 3d subshell fills after 4s. [1 marks]

Question 18 — Amount of substance

(a) D: Each formula unit gives 2 Al³⁺ and 3 SO₄²⁻, i.e. 5 ions: 0.10 × 5 = 0.50 mol. [1 marks]

Question 19 — Amount of substance

(a) C: %O = 3 × 16.0 / 100.1 × 100% = 47.95% ≈ 48.0%. [1 marks]

Question 20 — Amount of substance

(a) A: Mole ratio = 40.0/12 : 6.7/1 : 53.3/16 = 3.33 : 6.7 : 3.33 = 1 : 2 : 1 → CH₂O. [1 marks]

Question 21 — Amount of substance

(a) B: n = pV / RT = (1.00 × 10⁵ × 2.00 × 10⁻³) / (8.314 × 300) = 0.080 mol. [1 marks]

Question 22 — Amount of substance

(a) B: M = density × molar volume = 1.96 × 24.0 = 47.0 g mol⁻¹. [1 marks]

Question 23 — Redox and electrochemistry

(a) B: Q = It = 3 600 C, n(e⁻) = 3 600 / 96 500 = 0.0373 mol, Cu²⁺ + 2e⁻ → Cu so n(Cu) = 0.018 65 mol, m = 1.18 g. [1 marks]

Question 24 — Experimental data processing

(a) B: Uncertainty = 0.05 / 25.00 × 100% = 0.20%. [1 marks]

Question 25 — Energetics

(a) C: Atom economy = Mr of desired product / sum of Mr of all reactants = 88 / (20 + 24 + 44) = 88 / 132 = 66.7%; total reactant Mr is taken as 132. [1 marks]

Question 26 — Amount of substance

(a) B: N₂ and H₂ are in the exact 1 : 3 ratio, so n(NH₃) = 2 × 3.0 = 6.0 mol. [1 marks]

Question 27 — Energetics

(a) A: ΔH = bonds broken (2×436 + 498 = 1370) − bonds formed (4×464 = 1856) = −486 kJ mol⁻¹. [1 marks]

Question 28 — Amount of substance

(a) B: n = 0.24 / 24 = 0.010 mol, M = 0.30 / 0.010 = 30.0 g mol⁻¹. [1 marks]

Question 29 — Amount of substance

(a) B: n = 0.010 + 0.030 = 0.040 mol, V = 0.100 dm³, c = 0.40 mol dm⁻³. [1 marks]

Question 30 — Kinetics

(a) B: 80 / 20 = 4 half-lives, so (1/2)⁴ = 1/16 = 6.25% remains. [1 marks]

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