Let's set one up ConcentrationPCl 5 ↔PCl 3 + Cl 2 Initial8.7x10 -3 0.2980 Change-2x10 -3 +2x10 -3 Equilibrium6.7x10 -3 0.3002x10 -3 Since the concentration of Cl 2 we know has changed by 2x10 -3, the balanced reaction tells us that since it is a 1-1-1 reaction that the reactants decompose by 2x10 -3 and the products concentration increases by 2x10 -3
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