What Percentage of PCl5 Will Decompose at 523K?

[rcrx]

For the reaction at 523K PCl5 (g) <-> PCl3 (g) + Cl2 (g) and Kp = 0.500

What percentage of PCl5(g) will decompose if 0.100 atm of PCl5(g) is placed in a closed vessel at 523K?

I am unsure of how to approach this problem, if anyone could give some insight I would greatly appreciate it.

 

[chemisttree]

Look at your definition of Kp. All will become apparent.