WAEC Chemistry 2014 Objective — Question 30

Question 30 of 50 from the West African Examinations Council (WAEC) Chemistry 2014 Objective paper, with the correct answer and a full explanation.

In which of the following experimental set-ups would the rate of evolution of hydrogen gas be fastest?

A. Mg + HCl
B. Fe + HCl
C. Zn + HCl
D. Ca + HClCorrect

Explanation

The question indirectly demands the most reactive of the metals given. Based on the reactivity series (K,Na,Ca,Mg,Al,Zn,Fe,Sn,Pb,H,Cu — decreasing reactivity), calcium is the most reactive metal given, so its reaction with HCl produces hydrogen gas fastest.

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