JAMB - Chemistry (1984 - No. 2)
20 cm\(^3\) of hydrogen gas are sparked with 20cm\(^3\) of oxygen gas in an endimoeter at 373k (100\(^0\)C) and 1 atmosphere. The resulting mixture is cooled to 298 K (25 oC) and passed over calcium chloride. The volume of the residual gas is
40 cm 3
20 cm 3
30 cm 3
10cm 3
5cm 3
Explanation
2H\(_2\) + O\(_2\) → 2H\(_2\)O
From the balanced equation: 2cm\(^3\) : 1cm\(^3\) 2cm\(^3\)
From the question,expected vol. reacted: 20cm\(^3\) 20cm\(^3\)
Actual volume that reacted: 20cm\(^3\) 10cm\(^3\) 20cm\(^3\) → Following the balanced equation i.e ratio 2 : 1 : 2
Volume of H\(_2\) remaining = Expected volume - Actual volume = 20 - 20 = 0cm\(^3\) ⇒ H\(_2\) was used up, hence it's the limiting reactant.
Volume of O\(_2\) remaining = Expected volume - Actual volume = 20 - 10 = 10cm\(^3\) ⇒ O\(_2\) was in excess, thus it was remaining
Residual volume of the O\(_2\) is 10cm\(^3\)
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