CGPET 2017 Solved Paper

∵N2O4⇌2NO2
Molar ratio =1:2
Also, only 20% of N2O4 gets decomposed means.
1 mole of N2O4 on dissociation give =0.2×2=0.4 moles of NO2
and 0.8 moles of N2O4 remain undissociated.
Thus,
Total number of moles at equilibrium =0.4+0.8=1.2 moles
∵ Total pressure (pt)=1atm (given)
According to Daltons law of partial pressure
Partial pressure of N2O4=X(N2O4)×pt
and partial pressure of NO2=X(NO2)×pt
Partial pressure of NO2=

0.4

1.2

×1=0.33