In the chemical reaction: Br2 (g) + Cl2 (g) ⇌ 2 BrCl (g) KP = 0.150 If there is initially 0.500 atm of BrCl and nothing else in a container, what direction does the reaction move:

The reaction moves to the left.

Explanation:

If there is only 0.500 atm of BrCl (g), the reaction can only move to the left.

Since there is not any of the substaces that are represented by the left side of the chemical equation, nothing can go to the right.

Since there is BrCl, and it is represented on the right side of the equilibrium equation, it must decompose to produce Br₂ (g) and Cl₂ (g).

You can represent that situation in a ICE table, which is a table that shows the Initial concentrations (or pressures), the Change, due to the chemical reaction, and the final Equilibrium concentrations (or pressures)

In this case that is:

Br₂ (g) + Cl₂ (g) ⇌ 2 BrCl (g)

I 0 0 0.500 atm

C + x + x - 2x

E x x 0.500atm - 2x

That means that at the equilibrium the pressure of BrCl (g) will be 0.500atm - 2x, and the pressures of Br₂ (g) and Cl₂ (g), each, will be x. Thus, part of the initial BrCl (g) reacts, which means that the reaction moves to the left.

Using that information and the equilibrium constant equation you can calculate the equilibrium pressures of each substance.