Question

Consider the following four equilibria at 298 K:

CH4(g) + 4S(s) ⇌ CS2(g) + 2H2S(g) Kp = 9.5 × 10-10

S(s) + F2(g) ⇌ SF2(g) Kp = 1.6 × 1053

C2F2(g) + 4H2(g) ⇌ 2CH4(g) + F2(g) Kp = 1.5 × 1020

S(s) + H2(g) ⇌ H2S(g) Kp = 7.2 × 105

Question 1 What is Kp at 298 K for the following equilibrium? 2CH4(g) + SF2(g) ⇌ C2F2(g) + H2S(g) + 3H2(g)

Question 2 What is Kp at 298 K for the following equilibrium? CS2(g) + 4H2(g) ⇌ CH4(g) + 2H2S(g)

Question 3 What is Kp at 298 K for the following equilibrium?   C₂F₂(g) + 5S(s) ⇌ 2CS₂(g) + SF₂(g)

Answer 1

Question 1 What is Kp at 298 K for the following equilibrium?

2CH4(g) + SF2(g) < ---- > C2F2(g) + H2S(g) + 3H2(g)

Solution :- we want SF2 on reactant side so reverse equation 2

C2F2 need to be on product side so reverse equation 3

New equations are as follows

SF2(g) < ------ > S(s) + F2(g) Kp = 1/1.6 × 10^53

2CH4(g) + F2(g) < ----- > C2F2(g) + 4H2(g) Kp = 1/1.5 × 10^20

S(s) + H2(g) < ---- > H2S(g) Kp = 7.2 × 10^5

Adding these equations by cancelling the similar species on opposite sides we get

2CH4(g) + SF2(g) < ---- > C2F2(g) + H2S(g) + 3H2(g)

Kp = (1/1.6*10^53)*(1/1.5*10^20)* 7.5*10^5

Kp = 3.13*10^-68

Question 2 What is Kp at 298 K for the following equilibrium? CS2(g) + 4H2(g) < ---- > CH4(g) + 2H2S(g)

Solution :-

Need CS2 on reactant side and CH4 and H2S on product side

So reverse equation 1

Use equation 4 and multiply it by 4

CS2(g) + 2H2S(g) < ------ > CH4(g) + 4S(s)   Kp = 1/9.5 × 10^-10

4S(s) + 4H2(g) < ---- > 4H2S(g) Kp = (7.2 × 10^5)^4

By adding these equations we get

CS2(g) + 4H2(g) < ---- > CH4(g) + 2H2S(g)

Kp = (1/9.5*10^-10) * (7.2*10^5)4

Kp = 2.83*10^32

Question 3 What is Kp at 298 K for the following equilibrium?   C₂F₂(g) + 5S(s) ⇌ 2CS₂(g) + SF₂(g)

Solution :-

We want C2F2 on reactant side so keep equation 3 as it is

Need SF2 on product side so keep equation 2 as it

Need CS2 on product side so need equation 1 as it and multiply by 2

Reverese equation 4 and multiply by 4

New equations are

2CH4(g) + 8S(s) < ---- > 2CS2(g) + 4H2S(g) Kp = (9.5 × 10^-10)^2

S(s) + F2(g) < ---- > SF2(g) Kp = 1.6 × 10^53

C2F2(g) + 4H2(g) < ---- > 2CH4(g) + F2(g) Kp = 1.5 × 10^20

4H2S(g) < ----- > 4S(s) + 4H2(g) Kp = (1/7.2 × 10^5)^4

By adding all these equations we get

C₂F₂(g) + 5S(s) < ---- > 2CS₂(g) + SF₂(g)

Kp = (9.5*10^-10)^2 * 1.6*10^53 *1.5*10^20 * (1/7.2*10^5)^4

      = 8.06*10^31