Chemistry: Equilibrium Math Question 3

Question

A₂B ↔ 2A + B

With this simple equation, if you start with 0.815 M A₂B, and at equilibrium 53% of it has decomposed, what is the equilibrium constant?

Answer 1

A2B < === > 2A + B

Initial A2B = 0.815 M

At equilibrium, 53% A2B decomposed = 0.53 x 0.815 M = 0.432 M

For every mole A2B decomposed, 2 moles A and 1 mole B are formed. Thus, at equilibrium you have...

0.846 M A and 0.432 M B and 0.815 - 0.432 = 0.383 M A2B

Keq = [A]²[B]/[A₂B] = (0.846)²(0.432)/(0.383)

Keq = 0.807