Question

A) For the reaction
CH₄(g) + H₂O(g) ---> 3H₂(g) + CO(g)
delta H° = 206.1 kJ and delta S° = 214.7 J/K
The equilibrium constant for this reaction at 325.0 K is _____
Assume that delta H° and delta S° are independent of temperature.

B) For the reaction
N₂(g) + 2O₂(g)-->2NO₂(g)
deltaH° = 66.4 kJ and deltaS° = -121.6 J/K
The equilibrium constant for this reaction at 327.0 K is _____
Assume that delta H° and delta S° are independent of temperature.

C) For the reaction

2HBr(g) ---> H₂(g) + Br₂(l)
deltaH° = 72.6 kJ and deltaS° = -114.5 J/K
The equilibrium constant for this reaction at 345.0 K is _______

Assume that delta H° and delta S° are independent of temperature

Answer 1

(A) First calculate the free energy change for the reaction using the formula given below:

G^o = H^o - TS^o

G^o = 206100 - (325)(214.7) = 136322.5 J = 136.32 KJ

Now, we will calculate equilibrium constant, Keq

G^o = - RT lnKeq

lnKeq = - G^o/ RT or Keq = e^{-Go/ RT}

Substitute the values,

lnKeq = - 136322.5 / (8.314) (325) = - 50.45

Keq = e^{- 50.45} = 1.23 x 10^-22

(B) G^o = H^o - TS^o

G^o = 66400 - (327)(-121.6) = 106163.2 J

lnKeq = - 106163.2 / (8.314) (327) = - 39.05

Keq = e^{- 39.05} = 1.098 x 10^-17

(C) G^o = H^o - TS^o

G^o = 72600 - (345)(-114.5) = 112102.5 J

lnKeq = - 112102.5 / (8.314) (345) = - 39.08

Keq = e^{- 39.08} = 1.06 x 10^-17