5 mole of PCl5 and 4 mole of neon are introduced in a vessel of 110litre and allowed to attain equilibrium at 250∘C. At equilibrium, the total pressure of reaction mixture was 4.678atm. Calculate degree of dissociation of PCl5 and equilibrium constant for the reaction.
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Solution
Ne
PCl5
PCl3
Cl2
Initial number of moles
4
5
0
0
Equilibrium number of moles
4
5−x
x
x
The total number of moles is n=PVRT=4.678×1100.0821×523=11.98 It is also equal to n=4+5−x+x+x=9+x Hence, x=2.98≃3 The degree of dissociation A=2.485=0.596
Ne
PCl5
PCl3
Cl2
Equilibrium number of moles
4
2
3
3
Equilibrium mole fraction
1/3
1/6
1/4
1/4
The equilibrium constant B=K=(1/4)2×4.6781/6=6×4.67816=1.75 100(A+B)=100(0.596+1.75)=235