Question

10. The equilibrium constant K_c for the reaction

H2(g) + Br2(g) ⇆ 2HBr(g)

is 2.180 × 10⁶ at 730°C. Starting with 2.20 moles of HBr in a 13.7−L reaction vessel, calculate the concentrations of H₂, Br₂, and HBr at equilibrium.

[H2]	=
[Br2]	=
[HBr]	=

Answer 1

The reaction is as shown below

The equilibrium constant

Calculate initial concentration of HBr

Let 2x M be the change in the concentration of HBr to reach equilibrium. Prepare an ICE table.

Initial concentration (M)	0.00	0.00	0.161
Change in concentration (M)	x	x	-2x
Equilibrium concentration (M)	x	x

Substitute values in the equilibrium constant expression

Since the value of the equilibrium constant is very large, approximate 0.161-2x to 0.161

Take square root on both sides

Hence, the equilibrium concentrations are calculated as shown below