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JAMB Chemistry 2021 Question 5

Question 5

Mole Concept and Stoichiometry

How many grams of hydrogen gas will be produced when 6g of magnesium ribbon dissolves in 500cm3 of 6m HCl?

  1. A.0.5g
  2. B.0.7g
  3. C.0.3g
  4. D.1.2g
Show the answer and explanation

Answer: A (0.5g)

Explanation

Mg + 2HCl → MgCl2 + H2. Mg = 6/24 = 0.25 mol and the acid (3 mol) is in excess, so 0.25 mol H2 = 0.25 × 2 = 0.5 g.