Question

In a chemical reaction, substrate molecule A is broken down to form one molecule of product B and one molecule of product C. The equilibrium constant, K, for this reaction is 0.5. If we start with a mixture containing only substrate A at a concentration of 1 M, what will be the concentration of A when the reaction reaches equilibrium?

Answer 1

Answer:

Concentration of A at equilibrium = 1 - 0.5 = 0.5 M

Explanation:

$A \leftrightharpoons B + C$

Equilibrium constant = 0.5

Initial concentration of A = 1 M

             $A \leftrightharpoons B + C$

Initial      1            0     0

At equi.  1-x         x      x

Equilibrium constant = $\frac{[B][C]}{[A]}$

$0.5 = \frac{x \times x}{1-x} \\0.5(1-x) = x^2\\0.5 -0.5x = x^2\\x^2+0.5x - 0.5 = 0$

on solving,

x = 0.5 M

Concentration of A at equilibrium = 1 - 0.5 = 0.5 M