# Equilibrium Problem

• Sep 18th 2010, 10:22 PM
jsu03
Equilibrium Problem
How large should the equilibrium constant be for the rxn: A + 2B <=> C + 2D so that all but 0.10% of A is converted into products when A and B are reacted in an initial molar ratio of 1:2?

Can someone help me w/this problem? I have no idea how to do it. I tried setting it up like this but confused:

K = [c][d]^2/ [a][b]^2 .....

Thanks! n the answer is 9.97 * 10^8
• Sep 24th 2010, 08:16 AM
Quote:

Originally Posted by jsu03
How large should the equilibrium constant be for the rxn: A + 2B <=> C + 2D so that all but 0.10% of A is converted into products when A and B are reacted in an initial molar ratio of 1:2?

Can someone help me w/this problem? I have no idea how to do it. I tried setting it up like this but confused:

K = [c][d]^2/ [a][b]^2 .....

Thanks! n the answer is 9.97 * 10^8

The initial concentrations of A , B , C and D are respectively x , 2x , 0 , 0 .

99.9 % of A is being converted into products. In equilibrium state,

A = x - 0.999x = 0.001x
B= 2x - 1.998x = 0.002 x
C= 0 + 0.999x =0.999x
D= 1.998x

$K=\frac{(0.999x)(1.998x)^2}{(0.001x)(0.002x)^2}$

The 'x' s will eventually cancel off.