Explanation:
From ideal gas equation we have
P1V1= n1RT1
at state 1
And
P2V2= n2RT2
at state 2
given the volume and pressure as constant
therefore we can write
n1/n2 = T2/T1
n2/n1 = T1/T2 = 1/4
Therefore the fraction of moles of gas escaped = 1-1/4 = 3/4
