Question

A mixture of gas contains N2 and C2H2. 20ml of this mixture is added to 70ml of O2 and
combustion is allowed to take place over Hg. After cooling, the volume of the gas is found to be
68.5ml. When the resulting gaseous mixture is passed through KOH solution, the volume of
the residual gas is 38.5ml. Calculate % composition of N2 in the mixture.​

Answer 1

Answer:

Let the mixture contain a,b and c mL of CO,CH

4

and N

2

in it. Therefore, a+b+c=20...(i)

The reactions during combustion of mixture are as follows:

CO+

2

1

O

2

→CO

2

CH

4

+2O

2

→CO

2

+2H

2

O(l)

N

2

+O

2

→No reaction

Thus, reduction in volume is 2b due to 2nd reaction and

2

a

due to 1st reaction.

Total CO

2

formed =a+b= volume absorbed by KOH

∴a+b=14...(ii)

and, (a/2)+2b = 13...(iii)

By equations (i),(ii) and (iii), a=10 mL, b=4 mL, c=6 mL

Hope it helps you!!