Given the following reactions, 2PCl₃(g) ⇌ 2P(g) + 3Cl₂(g) Kc = 0.0667
PCl₃(g) + Cl₂(g) ⇌ PCl₅(g) Kc = 4.0
Calculate Kc for the reaction below.
2P(g) + 5Cl₂(g) ⇌ 2PCl₅(g)

Question

Given the following reactions, 2PCl₃(g) ⇌ 2P(g) + 3Cl₂(g) Kc = 0.0667 PCl₃(g) + Cl₂(g) ⇌ PCl₅(g) Kc = 4.0 Calculate Kc for the reaction below. 2P(g) + 5Cl₂(g) ⇌ 2PCl₅(g)

Quizplus · Accepted Answer

To solve for Kc of the given reaction, we can combine the two given reactions and cancel out the intermediate species, Cl2(g) and P(g). 
First, we reverse the first equation: 
2P(g) + 3Cl2(g) ⇌ 2PCl3(g)
Taking the reciprocal of the equation gives: 
PCl3(g)/P2(g)Cl3(g) = 1/Kc1 = 15 
Next, we multiply the second equation by the appropriate factor to cancel out Cl2(g): 
2PCl3(g) + 2Cl2(g) ⇌ 2PCl5(g) 
Multiplying the first equation by 2 and adding it to the second equation, we get: 
2P2(g) + 6Cl2(g) ⇌ 2PCl5(g) 
Dividing by P2(g)Cl5(g) gives: 
PCl5(g)/P2(g)^2Cl5(g) = Kc2/Kc1 = 4/0.0667 = 60.006
Therefore, Kc for 2P(g) + 5Cl2(g) ⇌ 2PCl5(g) is: 
(PCl5(g))^2/(P2(g))^5(Cl2(g))^10 = Kc2 = (P2(g)^2(Cl5(g))^2)/(P2(g))^5(Cl2(g))^10 = 240.

Given the Following Reactions, 2PCl3(g) ⇌ 2P(g) + 3Cl2(g) Kc

Given the Following Reactions, 2PCl₃(g) ⇌ 2P(g) + 3Cl₂(g) Kc