Answer to Question #145835 in General Chemistry for Clifford Benitez

Question

Phosphorus trichloride is reacted with chlorine to produce phosphorus pentachloride. The reaction reaches equilibrium and the following data were obtained: Phosphorus trichloride = 0.711M, and phosphorus pentachloride = 0.173M. If the equilibrium constant, Kc = 0.500, evaluate the equilibrium concentration of

chlorine.

Answer 1

From the balanced equation and the coefficients it should be obvious that everything works on a one-to-one basis. So there should be 0.25 moles of PCl₃ and 0.25 moles of PCl₅ should have been consumed, so there are 0.40-0.25 moles = 0.15 moles of PCl₅ left.

 Therefore [PCl₅] = 0.15 moles = 0.015 moles/L

                                10.0 L

 [PCl₃] and [Cl₂] both are 0.25 moles each. Therefore their concentrations are identical as well.

 [PCl₃] = [Cl₂] = 0.25 moles = 0.025 moles/L

                            10.0 L