Chemical Equilibrium Part 2 Question #12

[Jessica Nunez 1I]

I'm a little confused on how to solve this problem that's in the Chemical Equilibrium Part 2 Module.

Consider the following reaction at 1200 K, for which you know Kc = 1.7 x 10-3.
Br2 (g) ⇌ 2 Br (g)
Your experimental setup is able to measure the equilibrium concentration of Br2 based on its color, but you are unable to measure the concentration of Br directly. If you measure at equilibrium [Br2] to be 1.02 x 10-4 M, calculate the equilibrium concentration of Br for this experiment.

A. [Br] = 8.7 x 10-8

B. [Br] = 1.7 x 10-7

C. [Br] = 4.2 x 10-4

D.None of the above

[Naama 1A]

We use the equilibrium constant expression: Kc=[Br]^2/[Br2]. In this case, we know Kc and [Br2], so we simply solve for the unknown [Br], which ends up being C.