Chemical and Ionic Equilibrium - Result Question 43

####43. (a) In the following equilibrium N2O4(g)2NO2(g) when 5 moles of each are taken, the temperature is kept at 298 K the total pressure was found to be 20 bar. Given that

ΔGf(N2O4)=100kJ,ΔGf(NO2)=50kJ

(i) Find ΔG of the reaction.

(ii) The direction of the reaction in which the equilibrium shifts.

(b) A graph is plotted for a real gas which follows van der Waals’ equation with pVm taken on Y-axis and p on X-axis. Find the intercept of the line where Vm is molar volume. (2004,4M)

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Solution:

  1. (a) N2O4(g)2NO2(g)

ΔG=2ΔGf(NO2)ΔGf(N2O4)=0

Also ΔG=RTlnK=0,K=1

Let the reaction shifts in forward direction.

N2O4(g)2NO2(g) Total  5x5+2x10+x pi:5x10+x×205+2x10+x×20 K=(5+2x)2(10+x)2×10+x5x×20=1 81x2+405x+450=0 x=1.66 and 3.33

Both values of x indicates that reaction actually proceeds in backward direction.

(b) (p+aVm2)(Vmb)=RT

(p+ap2(pV)2)(pVpb)=RT

[(pV2)p+ap2][(pV)b]=p(pV)2RT

p[pV2+ap](pVbp)=p(pV2)RT

But p=0

Intercept =RT(pV)3=(pV)2RT



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