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35 cm3 of hydrogen was sparked with 12 cm3 of oxygen at 110°C and 760mm...

Chemistry
JAMB 1997

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

  • A. 11%
  • B. 31%
  • C. 35%
  • D. 69%
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Correct Answer: Option B
Explanation

Reaction for the equation:

\(2H_{2} + O_{2} \to 2H_{2} O\)

\(2 vol : 1 vol : 2 vol\)

Hence, 2 volumes of Hydrogen is needed for the reaction with Oxygen to produce steam (water).

\(\therefore 12cm^{3} O_{2} \to 2 \times 12cm^{3} = 24cm^{3} H_{2}\)

\(\text{Excess of Hydrogen} : 35 cm^{3} - 24 cm^{3} = 11 cm^{3}\)

\(\text{% Hydrogen left after the reaction} = \frac{11}{35} \times 100% = \frac{220}{7} = 31.48% \)

\(\approxeq 31% \)


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