Question

What would be the pressure (in atm as nearest integer) of $O_2$ in the following experiment?

A collapsed bag of 30 litre capacity is partially blown up by the addition of 10 litre of $N_2$ at 0.965 atm at 298 K. Subsequently enough $O_2$ is pumped into the bag, so that at 298 K and external pressure of 0.990 atm, the bag contains full 30 litre.

Answer 1

Initial condition, $P_{N_2}=0.965atm,V=10litre,T=298K$

Now $O_2$ is introduced to expand the bag fully to 30 litre,$N_2$ also occupy 30 litre at 298 K.

For $N_2$ alone new pressure is to be calculated by:

$P_1{V}_1=P_2{V}_2$

$0.965\times 10=P_{N_2}\times 30$

$P_{N_2}=0.322$ atm (at 30 litre volume)

$P_{O_2}=P_T-P_{N_2}=0.990-0.32=0.668$ atm

So nearest integer is 1 atm.