Question

For the equilibrium PCl5(g)⇌PCl3(g)+Cl2(g), the equilibrium constant Kp is 0.497 at 500K. A gas cylinder at 500K is charged with PCl5(g) at an initial pressure of 1.66atm. Determine the equilibrium pressure of all species at this temperature.

Answer 1

`p_(PCl_3)=0.693atm\\\\p_(Cl_2)=0.693atm\\\\p_(PCl_5)=0.967atm`

Step-by-step explanation:

Hello,

In this case, for the given reaction, the equilibrium expression is:

`Kp=(p_(PCl_3)p_(Cl_2))/(p_(PCl_5))`

But in terms of the reaction extent
`x` can also be written as:

`Kp=(x*x)/(p_0-x)`

Whereas the initial pressure is 1.66 atm. Thus, we write:

`0.497=(x^2)/(1.66atm-x)`

And solving for
`x` we obtain:

`x=0.693atm`

Therefore, the pressure of each species at equilibrium is:

`p_(PCl_3)=x=0.693atm\\\\p_(Cl_2)=x=0.693atm\\\\p_(PCl_5)=1.66atm-0.693atm=0.967atm`

Best regards.