A sample of hydrogen gas was collected over water at 21 ° C and 685 mm Hg. The volume of the container was 7.80 L. Calculate the mass of H 2 ( g ) collected (vapour pressure of water = 18.6 mm Hg at 21 ° C )

Question

A sample of hydrogen gas was collected over water at 21 ° C and 685 mm Hg. The volume of the container was 7.80 L. Calculate the mass of H 2 ( g ) collected (vapour pressure of water = 18.6 mm Hg at 21 ° C ), 0.283 g, 0.570 g, 0.589 g, 7.14 g

MARKS App · Accepted Answer

The volume of H 2 at STP V 2 = P 1 V 1 T 1 × T 2 P 2 Here vapour pressure of H 2 at 21 ° C = 685 mm – 18.6 mm = 666.4 mm So V 2 = 666.4 mm Hg × 7 .80 L × 273 K 294 K × 760 mm = 6.38 L At STP 22 .4 L H 2 weight = 2 g So, at STP 6 .38 L H 2 weigh = 2 g × 6 .38 L 22 .4 L = 0 .570 g

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