Question

How much reaction is complete when Kc = 10^30

Answer 1

The percentage varies with the reaction but with Kc = 10^30 the reaction is far to the right. For a 1:1 reaction; i.e., A + B ==> AB, then
Kc = (AB)/(A)(B) = 10^30
.....................A + B ==> AB
I....................1.....1..........0
C..................-x....-x..........x
E..................1-x...1-x.........x
Kc = 1E30 = (AB)/(A)(B) = (x)/(1-x)(1-x) = 1E30
x/(1 -2x + x^2) = 1E30
(x) = 1E30 - 2E30x + 1E30x^2
(x) on the left is so small compared to 2E30x so the equation becomes
0 = 1E30 - 2E30x + 1E30x^2. Solve with the quadratic formula and x = 1 and mathematically we have 1/(1-1)(1-1) = 1/0 so the percentage is infinite. However, x = 1 is really x = 0.9999999999999 so
x = 0.99999999 and 1-x = 0.0000001.
Plug into the Kc expression as [0.9999999/0.00000001*0.000000001]*100 = ?? a huge number