Question

Consider the reaction. PCl5(g)↽−−⇀PCl3(g)+Cl2(g) K=0.042 The concentrations of the products at equilibrium are [PCl3]=0.18 M and [Cl2]=0.30 M . What is the concentration of the reactant, PCl5, at equilibrium?

Answer 1

Answer: The equilibrium concentration of
`PCl_5` is 1.285 M.

Step-by-step explanation:

The chemical equation for the decomposition of phosphorus pentachloride follows:

`PCl_5(g)\rightleftharpoons PCl_3(g)+Cl_2(g)`

The expression for equilibrium constant is given as:

`K_c=([PCl_3][Cl_2])/([PCl_5])`

We are given:

`K_c=0.042`

`[PCl_3]=0.18M`

`[Cl_2]=0.30M`

The concentration of solid substances are taken to be 1. Thus, they do not appear in the equilibrium constant expression.

Putting values in above equation, we get:

`0.042=(0.18* 0.30)/([PCl_5])`

`[PCl_5]=1.285`

Hence, the equilibrium concentration of
`PCl_5` is 1.285 M.