Question

When 0.040 mol of PCl5 is heated to 250 oC in a 1.0 L vessel, an equilibrium is established in which the concentration of Cl2 is 0.025 M. Find the equilibrium constant for the reaction. PCl5(g) ⇌ PCl3(g) + Cl2(g)

Answer 1

To determine the equilibrium constant (Kc) for the reaction PCl5(g) ⇌ PCl3(g) + Cl2(g), one can use the given concentration of Cl2 to calculate the changes in concentrations of PCl5 and PCl3 at equilibrium and then apply these to the Kc expression.

Step-by-step explanation:

Finding the Equilibrium Constant

To find the equilibrium constant (Kc) for the decomposition of PCl5 into PCl3 and Cl2, we can write the expression for Kc based on the balanced chemical equation:

PCl5(g) ⇌ PCl3(g) + Cl2(g)

Kc = [PCl3][Cl2] / [PCl5]

Given the equilibrium concentration of Cl2 is 0.025 M and the initial amount of PCl5 is 0.040 mol in a 1.0 L vessel, we can calculate the changes in concentration of PCl5 and PCl3 at equilibrium using the ICE (Initial, Change, Equilibrium) table method.

Initially, [PCl5] = 0.040 M, [PCl3] = 0, [Cl2] = 0.
At equilibrium, [PCl5] = 0.040 M - x, [PCl3] = x, [Cl2] = x = 0.025 M.
Now, we can solve for x which represents the concentration of PCl3 and the change in concentration of PCl5.

After finding x, we can substitute the equilibrium concentrations into the Kc expression to find the equilibrium constant for the reaction.