Question

part b.

Determine the equilibrium constant, Kgoal, for the reaction

4PCl5(g)⇌P4(s)+10Cl2(g),    Kgoal=?

by making use of the following information:

P4(s)+6Cl2(g)⇌4PCl3(g),       K1=2.00×1019

PCl5(g)⇌PCl3(g)+Cl2(g),       K2=1.13×10−2

Express your answer numerically.

Answer 1

Solution :-

In the final equation we have P4 on the product side therefore we need to reverse the equation 1

And multiply equation 2 by 4 to get the 4 PCl5

After reversing the equation the Kc for the new equation is the inverse of the K1

And multiplying second equation by 4 means k for the new eequation is (K2)^4

Then add both equations by cancelling the similar species on the opposite sides and the K values are multipled.

Therefore new equations are as follows

4PCl3(g) ⇌ P4(s)+6Cl2(g)               1/K1=1/2.00×1019

4PCl5(g)⇌4PCl3(g)+4Cl2(g),            (K2)^4=(1.13×10−2)^4

___________________________________________________

4PCl5(g) ⇌P4(s) + 10 Cl2(g)         K_goal = (1/K1)*(K2)^4

Therefore K_goal = (1/2.00×1019)*(1.13*10^-2)^4 = 8.15*10^-28

Therefore equilibrium constant K_goal = 8.15*10^-28