# Problem: A 0.72-mol sample of PCl 5 is put into a 1.00-L vessel and heated. At equilibrium, the vessel contains 0.40 mol of PCl3(g) and 0.40 mol of Cl2(g). Calculate the value of the equilibrium constant for the decomposition of PCl5 to PCl3 and Cl2 at this temperature.

###### FREE Expert Solution

We are being asked to calculate the equilibrium constant, Kc for the given equilibrium reaction:

PCl5 (g)  Cl2 (g) + PCl(g)

When dealing with equilibrium and Kp:

Kc → equilibrium units are in molarity
Kc is an equilibrium expression:

$\overline{){{\mathbf{K}}}_{{\mathbf{c}}}{\mathbf{=}}\frac{\mathbf{products}}{\mathbf{reactants}}}$

only aqueous and gaseous species are included in the equilibrium expression
▪ the coefficient of each compound in the reaction equation will be the exponent of the concentrations in the equilibrium expression

Given:

Initial Concentrations:

[PCl5] = 0.72 mol / 1L = 0.72 M

In order to calculate the equilibrium concentrations of species, we need to use an ICE Chart

Since x is equal to 0.40 M, the concentration of PCl5 at equilibrium is:

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###### Problem Details

A 0.72-mol sample of PCl 5 is put into a 1.00-L vessel and heated. At equilibrium, the vessel contains 0.40 mol of PCl3(g) and 0.40 mol of Cl2(g). Calculate the value of the equilibrium constant for the decomposition of PCl5 to PCl3 and Cl2 at this temperature.