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CIE · IGCSE · Chemistry

Oxidation states and oxidation number rules
Practice Questions

20 CIE IGCSE Chemistry questions on Oxidation states and oxidation number rules, each with instant feedback and a full examiner-style mark scheme.

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Try 2 sample questions on Oxidation states and oxidation number rules

Question 1 · 1 mark · Difficulty 1/3

Which of the following correctly describes a reducing agent in a redox reaction?

  1. It accepts electrons and is itself oxidised.
  2. It accepts electrons and is itself reduced.
  3. It donates electrons and is itself reduced.
  4. It donates electrons and is itself oxidised.
Show answer & explanation
✓ Answer: DIt donates electrons and is itself oxidised.
A reducing agent donates electrons to another species, causing that species to be reduced. In doing so, the reducing agent loses electrons and is therefore oxidised itself. Option A describes an oxidising agent. Options C and D mix up electron transfer direction with the fate of the agent.
Question 2 · 1 mark · Difficulty 2/3

What is the oxidation state of sulfur in H₂SO₄?

  1. -2
  2. +4
  3. +6
  4. +2
Show answer & explanation
✓ Answer: C+6
+6 is correct: H is +1 (×2 = +2), O is -2 (×4 = -8), so S = 0 - (+2) - (-8) = +6. Option A (+4) corresponds to SO₂, a common confusion. Option C (+2) is not a typical sulfur state in common acids. Option D (-2) is the oxidation state of sulfide ions, not sulfur in an acid.
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CIE IGCSE Chemistry: Oxidation states and oxidation number rules FAQ

How many CIE IGCSE Chemistry questions on Oxidation states and oxidation number rules are there on Kramizo?
Kramizo currently has 20 exam-board-aligned practice questions on Oxidation states and oxidation number rules for CIE IGCSE Chemistry, with new questions added every week. Each question gives you instant feedback and a full examiner-style mark scheme that tells you exactly what would earn marks on a real CIE paper. The questions span the full difficulty range — from straightforward recall (level 1) right up to multi-step reasoning and evaluation (level 3) — so the bank works for first-pass revision and final exam-week stress testing alike.
Is Kramizo free for CIE IGCSE students preparing for Chemistry?
Yes — completely free. Every student gets 45 questions a day on the free plan, with no card required and no trial countdown. That free quota works across every subject and every topic in our bank, so you can mix Oxidation states and oxidation number rules practice with other Chemistry topics or even switch to a totally different CIE subject without paying anything. Kramizo's optional Pro plan removes the daily cap and adds detailed progress analytics, but the free tier is the real product — used by thousands of GCSE, IGCSE and CSEC students.
Are the Oxidation states and oxidation number rules questions aligned to the official CIE IGCSE Chemistry syllabus?
Every question is written against the published CIE IGCSE Chemistry specification, including the exact command words (state, describe, explain, calculate, evaluate, etc.), mark allocations, and difficulty tier you'd see on a real CIE paper. Explanations are written in the style of official examiner mark schemes — they tell you what is being awarded marks and why distractors are wrong, not just whether you got it right. The bank is continually refined to match the latest syllabus updates from CIE.
How is Oxidation states and oxidation number rules typically tested on CIE IGCSE Chemistry papers?
Oxidation states and oxidation number rules appears across multiple question types on real CIE IGCSE Chemistry papers — most commonly as multiple-choice questions in the objective section, structured short-answer questions in the main paper, and occasionally as part of an extended response. Kramizo's practice bank reflects that mix: 4-option MCQs, true/false statements, fill-in-the-blank key terms, multi-select questions, and ordering questions. Working through the bank gives you exposure to every question style examiners actually use.

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