# 1. For the reaction, #PCl_(3(g))+Cl_(2(g)) rightleftharpoons PCl_(5(g))#, #K_c = 96.2 # at 400 K. If the initial concentrations are 0.22 mol/L of #PCl_3# and 0.42 mol/L of #Cl_2#, what are the equilibrium concentrations of all species?

##### 1 Answer

So, you know that you're dealing with an equilibrium reaction that has its equilibrium constant equal to **96.2** at a certain temperature.

The fact that *larger than one* tells you that the reaction will favor the product, **decrease**.

At the same time, the concentration of **increase**. Use an **ICE table** to help you determine the equilibrium concentrations for your reaction

**I**.....0.22...........0.42.................0

**C**.....(-x).............(-x)..................(+x)

**E**...0.22-x.......0.42-x................x

By definition, the equilibrium constant will be equal to

Rearrange this equation to quadratic form

This equation will produce two solutions for

The first solution is eliminated because it will result in *negative* equilibrium concentrations for

**SIDE NOTE** *I've left the answers with three sig figs*.