WAEC Chemistry 2018 Objective — Question 3

Question 3 of 50 from the West African Examinations Council (WAEC) Chemistry 2018 Objective paper, with the correct answer and a full explanation.

Which of the following equations represents a redox reaction?

A. AgNO₃(aq)+KCl(aq)→AgCl(s)+KNO₃(aq)
B. HNO₃(aq)+NaOH(aq)→NaNO₃(aq)+H₂O(l)
C. CaCO₃(s)→CaO(s)+CO₂(g)
D. 2H₂S(g)+SO₂(g)→2H₂O(l)+3S(s)Correct

Explanation

In 2H₂S+SO₂→2H₂O+3S, sulphur's oxidation state changes in both reactants (H₂S is oxidised, SO₂ is reduced), making it the redox reaction; the others are simple precipitation, neutralisation, or decomposition.

Sign up free to unlock

Score tracking
Practice history
Saved questions
Progress dashboard
Personalized sessions
Weak-topic breakdown

…and/or go further with premium services and No Ads.

Create free account

More questions from Chemistry 2018 Objective More Chemistry past papers