Concept :
The total pressure and partial pressure are proportional to the number
of moles in the system.
Explanation : Total pressure = 0.8 atm at 20∘C
initial partial pressure of these gases
pp of O2=0.83=0.26atm
pp of H2=0.26×2=0.52 atm
Given:- yield = 80%
therefore, 80% of original molecules left unreacted
∴ Partial pressure of original gases after reaction.
H2=0.52×0.20=0.104atm
O2=0.36×0.20=0.052 atm
Or the Basis of strichiometry, amount of H2O formed will be equal to
the amount of H2 that realized therefore,
0.52×0.80=0.416atm
Total pressure at 20∘C=
Sum of partial pressure of gases
PT(20∘C)=0.104+0.052+0.416
=0.572atm
Pressure at 120∘C:−
P(120∘C)=0.57×3.93293=0.76atm