Question

A mixture initially contains A, B, and C in the following concentrations: [A] = 0.300 M , [B] = 1.30 M , and [C] = 0.400 M . The following reaction occurs and equilibrium is established: A+2B⇌C At equilibrium, [A] = 0.170 M and [C] = 0.530 M . Calculate the value of the equilibrium constant, Kc.

Answer 1

                A +     2 B <=======>   C

I              0.3        1.3                      0.4

C             -x           -2x                   +x

E            0.3-x       1.3-2x                0.4 +x

but at equilibrium A is already given

0.3-x = 0.17

x = 0.3 - 0.17 = 0.13

[B] = 1.3-2x   = 1.3 - 2(0.13)   = 1.3 - 0.26 = 1.04M

[C] = 0.4 + 0.13 = 0.53

Kc = [C] / [A] [B]²

Kc = [0.53] / [0.17][1.04]²

= 0.53 / 0.1838

Kc = 2.88