20 cm 3 of hydrogen gas are sparked with 20cm 3 of oxygen gas in an endimoeter at 373k (100 oC) 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

A.

40 cm 3

B.

20 cm 3

C.

30 cm 3

D.

10cm 3

E.

5cm 3

Correct answer is D

2H2 + O2 ------2H2O
2V 1V 2V
20cm3 20cm3 -------
20cm3 10cm3 20cm3
Residual gas = 20cm3 - 10cm3 of 02 = 103