An equilibrium mixture at 300K contains N2O4 and NO2 at 0.28 and 1.1 atm pressures respectively.
N2O4(g)⇌2NO2(g)
The equilibrium constant
Kp=[pNO2]2pN2O4=(1.1)20.28=4.32atm
If the volume of the container is doubled, the partial pressures of each gaseous component is reduced to half.
PN2O4=0.282=0.14 atm.
PNO2=1.12=0.55 atm
When new equilibrium is stabilized, x atm of N2O4 have reacted to form 2x atm of NO2.
N2O4(g)⇌2NO2(g)
PN2O4=0.282=0.14−x atm.
PNO2=1.12=0.55+2x atm
Kp=[pNO2]2pN2O4
Kp=(0.55+2x)2(0.14−x)=4.32
0.30+1.1x+4x2=0.605−4.32x
4x2+5.42x−0.302=0
This is quadratic equation with solution.
x=−b±√b2−4ac2a
x=−(5.42)±√(5.42)2−4(4)(−0.302)2(4)
x=−5.42±5.858
x=−5.42±5.858
x=0.045 or x=−1.41
The value -1.41 is discarded as it will lead to negative value of pressure.
x=0.045
pN2O4=0.14−x=0.14−0.045=0.095atm
pNO2=0.55+2x=(0.55+2×0.045)=0.64atm
The new equilibrium pressure of the two gases is 0.64 atm.