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JAMB Chemistry 1984 Question 2

Question 2

Gas Laws

20 cm3 of hydrogen gas are sparked with 20 cm3 of oxygen gas in an endiometer at 373 K (100°C) and 1 atmosphere. The resulting mixture is cooled to 298 K (25°C) and passed over calcium chloride. The volume of the residual gas is

  1. A.40 cm3
  2. B.20 cm3
  3. C.30 cm3
  4. D.10 cm3
  5. E.5 cm3
Show the answer and explanation

Answer: D (10 cm3)

Explanation

2H2 + O2 → 2H2O, so 20 cm3 of hydrogen uses only 10 cm3 of oxygen. The water is condensed and absorbed by calcium chloride, leaving 10 cm3 of unused oxygen.