When this system is at equilibrium at a certain temperature PCl5(g) ⇋ PCl3(g) + Cl2(g), the concentrations are found to be [PCl5] = 0.40 M, [PCl3] = [Cl2] = 0.20. If the volume of the container is suddenly halved at the same temperature, what will be the new equilibrium concentration of PCl5?

Respuesta :

Answer:

The new concentration of [tex]PCl_5[/tex] will be 0.9 M.

Explanation:

[tex]PCl_5(g)\rightleftharpoons PCl_3(g) + Cl_2(g)[/tex]

The equilibrium concentration of all species:

[tex][PCl_5]=0.40 M[/tex]

[tex][PCl_3]=[Cl_2]=0.20 M[/tex]

The equilibrium constant's expression can be written as:

[tex]K_c=\frac{[PCl_3][Cl_2]}{[PCl_5]}[/tex]

[tex]K_c=\frac{0.20 M\times 0.20 M}{0.40 M}=0.1[/tex]

On halving the volume of the container, the concentration will get doubled;

[tex]PCl_5(g)\rightleftharpoons PCl_3(g) + Cl_2(g)[/tex]

0.80 M                                         0.40M   0.40 M

[tex]Q_c=\frac{0.40 M\times 0.40 M}{0.80 M}=0.2[/tex]

[tex]Q_c>K_c[/tex]

Reaction will go backward.

[tex]PCl_5(g)\rightleftharpoons PCl_3(g) + Cl_2(g)[/tex]

Initially

0.80 M                                         0.40M   0.40 M

After reestablishment of an  equilibrium

(0.80+x) M                                         (0.40-x)M   (0.40-x) M

So, the equilibrium expression for above reaction can be written as :

[tex]K_c=\frac{(0.40-x) M\times (0.40-x) M}{(0.80+x) M}[/tex]

[tex]0.1=\frac{(0.40-x) M\times (0.40-x) M}{(0.80+x) M}[/tex]

x = 0.1 M

The new concentration of [tex]PCl_5[/tex] will be:

[tex][PCl_5]=(0.80+x) M=(0.80+0.1) M = 0.90[/tex]