Chemistry · Redox reactions · chapter 7 of 9

Class 11 Chemistry Chapter 7: Redox Reactions Assertion-reason questions with answers

2 assertion-reason questions on Redox Reactions, each with its answer and the reason, written from the NCERT chapter. For school exams on the CBSE pattern, JEE Main and NEET, which are set from the same NCERT chapter. Open a question's solution to check your working; then take the free test to find your next chapter. Each question gives an Assertion (A) and a Reason (R); choose how they stand to each other.

Question 1
Assertion (A): When a zinc strip is placed in copper sulphate solution, zinc acts as the reducing agent. Reason (R): Zinc donates electrons to Cu²⁺ ions, which are reduced to copper.
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Answer: (a) Both A and R are true, and R is the correct explanation of A.

Both are true. Zn → Zn²⁺ + 2e⁻ and Cu²⁺ + 2e⁻ → Cu; a reducing agent is an electron donor, so the transfer of electrons from zinc to Cu²⁺ is exactly why zinc is the reductant.

Question 2
Assertion (A): The decomposition of calcium carbonate into calcium oxide and carbon dioxide is not a redox reaction. Reason (R): Calcium, an alkaline earth metal, has the oxidation number +2 in all its compounds.
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Answer: (b) Both A and R are true, but R is not the correct explanation of A.

Both are true, but R does not explain A. A holds because no element changes its oxidation number: Ca stays +2, C +4 and O −2. That calcium is +2 says nothing about carbon and oxygen.

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