plumiOxidation numbers: Edexcel International A Level Chemistry questions
Edexcel International A Level Chemistry past-paper questions on 8.A.1 Oxidation numbers, 2019–2025, with mark schemes and examiner’s reports where available.
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All 36 questions on Oxidation numbers, as a list
- June 2025, AS Unit 2, Q5 (1 mark): Which is the correct order of increasing oxidation number of nitrogen in – and NH3 ? NO , NO3 A NH3 NO NO3 – B NH3 NO3 – NO C NO NH3 NO3 – D NO3 – NH3 NO
- June 2025, AS Unit 3, Q4(a) (2 marks): Chlorine is generated by the vigorous redox reaction between concentrated hydrochloric acid and potassium manganate(VII). The chlorine moves through the apparat
- June 2025, Unit 5, Q2(d) (1 mark): Which row shows the correct changes in oxidation states? (1) manganese iron II → VII III → II A II → VII II → III B VII → II III → II C VII → II II → III D Use
- June 2025 (A), Unit 5, Q3(a) (1 mark): What is the change in oxidation number of a carbon atom when this reaction occurs? (1) A –1 B +1 C +3 D +4
- January 2025, AS Unit 2, Q17(a)(i) (2 marks): Deduce the oxidation number changes for manganese and carbon. (2) Manganese from to Carbon from to
- January 2025, Unit 5, Q20(a)(iv) (2 marks): State whether or not the reaction in Reaction 4 is a redox reaction. Justify your answer using oxidation numbers. (2)
- June 2024, AS Unit 2, Q18(b)(i) (1 mark): State the meaning of the Roman numerals in chlorate(V) and chlorate(VII). (1)
- June 2024, AS Unit 2, Q18(b)(ii) (1 mark): State the oxidation number of chlorine in chlorine dioxide. (1)
- June 2024, AS Unit 2, Q18(b)(iii) (2 marks): In Step 2, compound A undergoes disproportionation. Deduce the possible range of oxidation numbers for the chlorine in compound A. Justify your answer. (2)
- June 2024, Unit 5, Q3(a) (1 mark): Which shows the changes in the oxidation states for iron and manganese? (1) Iron Manganese II → III VII → II A II → III VII → IV B III → II II → VII C III → II
- June 2024 (R), AS Unit 2, Q14 (1 mark): Which species contains an element with an oxidation number of +4? A CrO4 2– B MnO4 2– C H2SO4 D Na2CO3
- January 2024, AS Unit 2, Q6 (1 mark): Which compound does not contain an element with an oxidation number of –1? A HF B NaH C H2O2 D CH4
- January 2024, AS Unit 2, Q7 (1 mark): Which reaction involves the oxidation of a Group 7 element? A Br2 + F2 → 2BrF B U + 3ClF3 → UF6 + 3ClF C 2F2 + 2H2O → 4HF + O2 D KCl + H2SO4 → HCl + KHSO4 Use t
- January 2024, Unit 5, Q16(a)(i) (1 mark): Justify the assignment of the oxidation state of +5 to manganese in H3MnO4 using oxidation numbers. (1)
- October 2023, Unit 5, Q2 (1 mark): In which of these pairs does the transition metal have the same oxidation number? A CrO2Cl2 and [Cr(NH3)4Cl2]+ B [Cu(NH3)2]+ and [CuCl4]2− C Mn2O3 and MnO2 D VO
- June 2023, AS Unit 2, Q8 (1 mark): In which pair of compounds is the stated element in the same oxidation state? A chlorine in Cl2O7 and Ca(ClO3)2 B chromium in K2Cr2O7 and K2CrO4 C manganese in
- June 2023, AS Unit 2, Q9 (1 mark): What is the formula of barium(II) ferrate(VI)? A Ba2FeO3 B BaFeO3 C Ba2FeO4 D BaFeO4
- January 2023, AS Unit 2, Q7 (1 mark): Which ion contains vanadium with an oxidation number of +4? A VO2+ B VO2 + C VO3 – D VO4 3–
- January 2023, AS Unit 2, Q8 (1 mark): What is the formula of potassium manganate(VI)? A KMnO4 B K2MnO4 C K3MnO4 D K6Mn2O6 Use this space for any rough working. Anything you write in this space will
- January 2023, Unit 5, Q1 (1 mark): In which species does the transition metal have the lowest oxidation number? A [Cu(NH3)2]+ B [Fe(CN)6]3– C MnSO4 D Ni(CO)4
- January 2023, Unit 5, Q18(a) (1 mark): State the oxidation number of vanadium in Na3VO4 . (1)
- October 2022, AS Unit 2, Q13 (1 mark): − ? 13 What is the oxidation number of bromine in BrO3 A +1 B +3 C +5 D +7
- June 2022, AS Unit 2, Q4 (1 mark): What is the name of the compound with the formula KClO2 ? A potassium chlorate(II) B potassium chlorate(III) C potassium chlorate(IV) D potassium chlorate(V)
- January 2022, AS Unit 2, Q11 (1 mark): 2− ? 11 Which name is correct for the ion SO4 A sulfate(II) B sulfate(IV) C sulfate(VI) D sulfate(VIII)
- January 2022, AS Unit 2, Q12 (1 mark): In which compound is the oxidation number of nitrogen +5? A Ca(NO3)2 B Mg3N2 C N2O3 D NaNO2
- January 2022, Unit 5, Q9 (1 mark): The formulae of four ions are shown. Formula of ion 2− CrO4 AlO2 − [Fe(CN)6]4− [CrCl2(H2O)4]+ How many of these ions contain a metal with an oxidation number of
- October 2021, AS Unit 2, Q11 (1 mark): 3– ? 11 What is the oxidation number of phosphorus in the phosphate ion, PO4 A –3 B +3 C +5 D +7
- June 2021, AS Unit 2, Q5 (1 mark): What is the oxidation number of chromium in Na2Cr2O7? A +1 B +2 C +3 D +6
- June 2021, AS Unit 2, Q6 (1 mark): In an oxide of nitrogen, the oxidation number of nitrogen is +4. Which is the formula of the oxide? A N2O B N2O3 C N2O4 D N2O5
- June 2021, Unit 5, Q1 (1 mark): In which of the following pairs does the metal have different oxidation numbers? A CrO4 2− and Cr2O7 2− B CrO4 2− and CrO3Cl− C V2O5 and VO4 3− D VO2 + and VO2+
- January 2021, AS Unit 2, Q6(b) (1 mark): One of the reaction products is the gas H2S. What is the change in oxidation number of sulfur as H2S forms? (1) A −8 B −6 C −2 D +6
- January 2021, AS Unit 2, Q22(d)(i) (1 mark): Give the systematic name of KClO4 . (1)
- October 2020, AS Unit 2, Q7 (1 mark): In an oxide of potassium, the oxidation number of oxygen is –½. What is the formula of this oxide? A K2O B K2O2 C K2O3 D KO2 Use this space for any rough workin
- October 2020, Unit 5, Q14 (1 mark): Which species contains an element with the same oxidation number as bromine in KBrO3? A N2O5 B KMnO4 C K2FeO4 D Na2SO3
- October 2020, Unit 5, Q24(b)(ii) (1 mark): Two vanadium species exist in equilibrium in an aqueous solution. −(aq) + H2O(l) ⇌ VO2 VO3 +(aq) + 2OH−(aq) Deduce whether or not this is a redox reaction. Just
- June 2019, AS Unit 2, Q6 (1 mark): 2–, is 6 The oxidation number of sulfur in the sulfate ion, SO4 A −2 B +4 C +6 D +8 Use this space for any rough working. Anything you write in this space will
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