Fugacity: It is derived from Latin, expressed as fleetness or escaping ...

Effect of variables on equilibrium :
Effect of temperature:
G RT lnK
since ΔG depends only on temperature as the
0
298 298
pressure is fixed at 1.0 atmosphere, K value varies with temperature. It is not affected by
Pressure, Concentration, etc,. Variation of K with T is given by
ln K
d H
2
dT RT
Van't Hoff equation.
For endothermic reactions ΔH 0 is + ve as T increases K also increases. This
means that the equilibrium conversion is more at higher pressure.
For exothermic reactions ΔH 0 is –ve. Therefore K increases with T. Hence the
equilibrium conversion decreases as T increases. Eg. SO2 + 1/2 O2 ↔ SO3
Effect of pressure: Consider a reaction of ideal gases, then K = KyP Δn or Ky = K / P Δn
When Δn > 0. An increase in pressure decreases Ky. Hence equilibrium product
yield is less at high pressures
When Δn< 0. An increase in pressure increases Ky and equilibrium product
yield
pressure is required
C2H4 + H2O C2H5OH Δn = 1 – (1+1) = -1, Δn < 0
N2 + 3H2 2NH3 Δn = 2 – 4 = – 2 Δn < 0 Here high
When Δn = 0 Here pressure has no effect on reaction. For ideal gases the effect
of pressure depends on the variation of γ and Φ with pressure
Effect of Inert: Presence of inert has the opposite effect of increase of pressure.
Therefore when Δn > 0, addition of inert increases Ky and equilibrium
conversion
And Δn < 0, addition of inert decreases equilibrium conversion.
Effect of excess reactants: Presence of excess reactants increases equilibrium
conversion of the limiting reactant
Presence of products in feed: decreases the equilibrium conversion of reactants.
Eg. CH3COOH + C2H5OH CH3COOC2H5 + H2O
If water is added by 1.0 mole to the feed, equilibrium conversion of CH3COOH
reduces from 30% to 15%