WAEC Chemistry 2019 Objective — Question 6
Question 6 of 50 from the West African Examinations Council (WAEC) Chemistry 2019 Objective paper, with the correct answer and a full explanation.
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If 6.5 g of magnesium ribbon reacts completely with hydrochloric acid, how many grams of hydrogen gas would be liberated? Mg(s)+2HCl(aq)→MgCl2(aq)+H2(g) [H=1.0, Mg=24.0]
- A. 0.54gCorrect
- B. 0.70g
- C. 1.08g
- D. 1.40g
Explanation
Moles of Mg = 6.5/24 = 0.2708 mol. Mole ratio Mg:H2 = 1:1, so moles of H2 = 0.2708 mol. Mass of H2 = 0.2708 × 2 = 0.54 g.
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