OCR AS LEVEL CHEMISTRY A H032/02 DEPTH IN
CHEMISTRY VERIFIED QUESTION PAPER/ ACTUAL EXAM
QUESTIONS AND CORRECT ANSWERS WITH RATIONALES
GRADED A+ LATEST 2025/2026
Part 1 — (Physical & Inorganic Chemistry, kinetics, equilibria, bonding,
calculations)
Q1. Which of the following statements about ionisation energy is correct?
A. Ionisation energy increases down a group because nuclear charge increases.
B. Ionisation energy decreases across a period due to increased shielding.
C. Ionisation energy increases across a period due to increasing nuclear charge.
D. Ionisation energy is constant across a period.
Answer: C
Rationale: Across a period, nuclear charge increases while shielding by inner
electrons remains nearly constant, so the attraction on valence electrons increases
and ionisation energy rises.
Q2. The second ionisation energy of magnesium is higher than the first because:
A. The second electron is removed from the same orbital.
B. The remaining ion has a greater effective nuclear charge.
C. Shielding increases after the first ionisation.
D. The electron removed is farther from the nucleus.
Answer: B
Rationale: After removing one electron, Mg⁺ has fewer electrons but the same
nuclear charge; the effective nuclear attraction per electron increases, making the
second ionisation harder.
Q3. Which molecule is non-polar overall?
A. H₂O
B. CO₂
C. CHCl₃
,D. NH₃
Answer: B
Rationale: CO₂ is linear; although the C=O bonds are polar, the dipoles are equal
and opposite and cancel, giving a non-polar molecule.
Q4. Which best explains the high melting point of MgO compared to NaCl?
A. Smaller ionic radius of Na⁺
B. Higher charge and smaller ionic radius of Mg²⁺ and O²⁻
C. Covalent bonding in MgO
D. Greater van der Waals forces
Answer: B
Rationale: MgO has +2 and −2 ions; Coulomb’s law means higher charges and
smaller ionic radii produce much stronger ionic lattice energies than NaCl’s +1/−1
ions.
Q5. Oxidation state of sulfur in H₂SO₄?
Answer: +6
Rationale: Let S = x: 2(+1) + x + 4(−2) = 0 → x = +6.
Q6. Products when Cl₂ reacts with cold dilute NaOH:
Answer: NaCl and NaClO (hypochlorite)
Rationale: Cl₂ disproportionates in cold, dilute alkali: Cl₂ + 2NaOH → NaCl +
NaClO + H₂O.
Q7. 0.24 g Mg reacts with 50.0 cm³ of 1.0 mol dm⁻³ HCl. Which reagent is in
excess? (Mg + 2HCl → MgCl₂ + H₂)
Answer: HCl is in excess.
Rationale: n(Mg) = 0.24/24.3 = 0.00988 mol → HCl required = 2× = 0.01976
mol. HCl available = 0.0500 L ×1.00 = 0.0500 mol → excess.
, Q8. Which element has the largest atomic radius?
A. N B. O C. F D. C
Answer: D (C)
Rationale: Atomic radius decreases across a period; carbon (furthest left among
choices) is largest.
Q9. The standard enthalpy change of formation of CO₂ (−394 kJ mol⁻¹) is defined
as:
Answer: Enthalpy change when 1 mol CO₂ forms from its elements in their
standard states.
Rationale: That is the definition of standard enthalpy of formation.
Q10. For 2SO₂(g)+O₂(g)⇌2SO₃(g), expression for Kc?
Answer: Kc=[SO3]2[SO2]2[O2]K_c=\dfrac{[SO_3]^2}{[SO_2]^2[O_2]}Kc
=[SO2]2[O2][SO3]2
Rationale: Equilibrium constant uses product concentrations raised to
stoichiometric powers divided by reactants similarly.
Q11. A reaction is first order in A and second order in B. The rate law is:
A. rate = k[A][B]
B. rate = k[A]^1[B]^2
C. rate = k[A]^2[B]
D. rate = k[A]^2[B]^2
Answer: B
Rationale: “First order in A” means power 1 for [A]; “second order in B” means
power 2 for [B].
Q12. If temperature increases, what happens to Kc for an endothermic reaction?
A. Kc decreases
B. Kc increases
C. Kc unaffected
CHEMISTRY VERIFIED QUESTION PAPER/ ACTUAL EXAM
QUESTIONS AND CORRECT ANSWERS WITH RATIONALES
GRADED A+ LATEST 2025/2026
Part 1 — (Physical & Inorganic Chemistry, kinetics, equilibria, bonding,
calculations)
Q1. Which of the following statements about ionisation energy is correct?
A. Ionisation energy increases down a group because nuclear charge increases.
B. Ionisation energy decreases across a period due to increased shielding.
C. Ionisation energy increases across a period due to increasing nuclear charge.
D. Ionisation energy is constant across a period.
Answer: C
Rationale: Across a period, nuclear charge increases while shielding by inner
electrons remains nearly constant, so the attraction on valence electrons increases
and ionisation energy rises.
Q2. The second ionisation energy of magnesium is higher than the first because:
A. The second electron is removed from the same orbital.
B. The remaining ion has a greater effective nuclear charge.
C. Shielding increases after the first ionisation.
D. The electron removed is farther from the nucleus.
Answer: B
Rationale: After removing one electron, Mg⁺ has fewer electrons but the same
nuclear charge; the effective nuclear attraction per electron increases, making the
second ionisation harder.
Q3. Which molecule is non-polar overall?
A. H₂O
B. CO₂
C. CHCl₃
,D. NH₃
Answer: B
Rationale: CO₂ is linear; although the C=O bonds are polar, the dipoles are equal
and opposite and cancel, giving a non-polar molecule.
Q4. Which best explains the high melting point of MgO compared to NaCl?
A. Smaller ionic radius of Na⁺
B. Higher charge and smaller ionic radius of Mg²⁺ and O²⁻
C. Covalent bonding in MgO
D. Greater van der Waals forces
Answer: B
Rationale: MgO has +2 and −2 ions; Coulomb’s law means higher charges and
smaller ionic radii produce much stronger ionic lattice energies than NaCl’s +1/−1
ions.
Q5. Oxidation state of sulfur in H₂SO₄?
Answer: +6
Rationale: Let S = x: 2(+1) + x + 4(−2) = 0 → x = +6.
Q6. Products when Cl₂ reacts with cold dilute NaOH:
Answer: NaCl and NaClO (hypochlorite)
Rationale: Cl₂ disproportionates in cold, dilute alkali: Cl₂ + 2NaOH → NaCl +
NaClO + H₂O.
Q7. 0.24 g Mg reacts with 50.0 cm³ of 1.0 mol dm⁻³ HCl. Which reagent is in
excess? (Mg + 2HCl → MgCl₂ + H₂)
Answer: HCl is in excess.
Rationale: n(Mg) = 0.24/24.3 = 0.00988 mol → HCl required = 2× = 0.01976
mol. HCl available = 0.0500 L ×1.00 = 0.0500 mol → excess.
, Q8. Which element has the largest atomic radius?
A. N B. O C. F D. C
Answer: D (C)
Rationale: Atomic radius decreases across a period; carbon (furthest left among
choices) is largest.
Q9. The standard enthalpy change of formation of CO₂ (−394 kJ mol⁻¹) is defined
as:
Answer: Enthalpy change when 1 mol CO₂ forms from its elements in their
standard states.
Rationale: That is the definition of standard enthalpy of formation.
Q10. For 2SO₂(g)+O₂(g)⇌2SO₃(g), expression for Kc?
Answer: Kc=[SO3]2[SO2]2[O2]K_c=\dfrac{[SO_3]^2}{[SO_2]^2[O_2]}Kc
=[SO2]2[O2][SO3]2
Rationale: Equilibrium constant uses product concentrations raised to
stoichiometric powers divided by reactants similarly.
Q11. A reaction is first order in A and second order in B. The rate law is:
A. rate = k[A][B]
B. rate = k[A]^1[B]^2
C. rate = k[A]^2[B]
D. rate = k[A]^2[B]^2
Answer: B
Rationale: “First order in A” means power 1 for [A]; “second order in B” means
power 2 for [B].
Q12. If temperature increases, what happens to Kc for an endothermic reaction?
A. Kc decreases
B. Kc increases
C. Kc unaffected
