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JAMB Chemistry 1997 Question 1

Question 1

Gas Laws

35 cm3 of hydrogen was sparked with 12 cm3 of oxygen at 110°C and 760 mm Hg to produce steam. What percentage of the total volume of gas left after the reaction is hydrogen?

  1. A.11%
  2. B.31%
  3. C.35%
  4. D.69%
Show the answer and explanation

Answer: B (31%)

Explanation

2H2 + O2 → 2H2O: 12 cm3 of O2 uses 24 cm3 of H2 and makes 24 cm3 of steam (a gas at 110°C). 11 cm3 of H2 is left in a total of 35 cm3, so 11/35 × 100 ≈ 31%.