Question

An open vessel containing air is heated from 300 K to 400 K. The fraction of air originally present which goes out it is A) 3/4 B) 1/4 C) 2/3 D) 1/8

Answer 1

According to ideal gas equation

PV=nRT

n1 =1
T1 =300k,
T2=400k
n2=?

P1V1=n1 RT1 
P2 V2=n2RT

n1/n2 = T2/T1

1/n2 =400/300

n2=3/4

The fraction of air present in vessel after heating n2=3/4

The fraction of air which goes out of the vessel =1-3/4
=1/4

Answer 2

As the vessel is open the pressure remains constant and there is no change in the volume of vessel. Hence volume also constant.According to ideal gas equationPV=nRT n1 =1 T1 =300k, T2=400 k n2=? P1V1=n1 RT1 , P2 V2=n2RT n1/n2= T2/T1 1/n2 =400/300 n2=3/4 The fraction of air present in vessel after heating n2=3/4 The fraction of air which goes out of the vessel =1-3/4=1/4

Hope it helps you.