Question

Sumit evacuated a cylinder and filled in 4g of gas A at temperature 25˚C. Pressure was found to
be 1 atm. His friend Vineet, filled another 8g of gas B in the cylinder at the same temperature. The
final pressure was found to be 1.5 atm. The ratio of molecular masses of A and B (assuming ideal
gas behaviour) is
a) 1 : 1 b) 1 : 2 c) 1 : 3 d) 1 : 4

Answer 1

Using

PV= nRT

For gas A only

1 x V=nART

or

V = (4/MA)RT..............(1)

 

After addition of gas B.

1.5V=(nA+nB)RT

or

1.5V=(4/MA+8/MB)RT................(2)

Now dividing eq. (2) by e.q(1) and solving we get..

MA/MB= 1/2