eqilibrium summary

Question

Analysis of the mixture showed that at equilibrium the concentrations of PCl₃, Cl₂, and PCl₅ were 0.0175 M, and 0.118 M respectively. Calculate the value of K_c at this temperature.

PCl₅ (g) => PCl₃ (g) + Cl₂ (g)

Answer 1

PCl₅ (g) => PCl₃ (g) + Cl₂ (g)

Kc = [PCl₃][Cl₂] / [PCl₅]

You only provided the equilibrium concentrations for 2 of the species (0.0175 M and 0.118 M). We need the concentration of the other one. Then must plug in the values and solve for Kc.