[meg2442]

I dont know how to solve this problem.

K value at equilibrium is 630 at 546K. The solutions are at a constant volume and begin with equimolar amounts.

The expression is
PCl₅ <-> PCl₃ + Cl₂

What is the relationship between PCl₃ and Cl₂ at Eqm.

If they all start with x initially then the reactants will subtract and the products will add so I'm not sure what else to add to that? Wont PCl₃ and Cl₂ be the same if they start out the same and add the same amount?

[Donaldson Tan]

Below is the ICE table for equilibirum at hand. X is the initial concentration and Y is the change in concentration. The change in concentration follows the stoichiometric ratio predicted by the equilibrium reaction given by meg2422.

	Initial	Change	Eqbm
PCl5	X	-Y	X - Y
PCl3	X	+Y	X + Y
Cl2	X	+Y	X + Y

The concentration of Cl₂ indeed equals to the concentration of  PCl₃ at initial and equilibrium condition.