The equilibrium constant Kc for the decomposition of phosgene, COCl2, is 4.63x10^-3 at 527 C. Calculate the equilibrium partial pressure of all the components, starting with pure phosgene at 0.760 atm

Respuesta :

Answer: The partial pressure of the [tex]CO,Cl_2\text{ and }COCl_2[/tex] are 0.352 atm, 0.352 atm and 0.408 atm respectively.

Explanation:

We are given:

[tex]K_c=4.63\times 10^{-3}[/tex]

[tex]p_{COCl_2}=0.760atm[/tex]

Relation of [tex]K_p[/tex] with [tex]K_c[/tex] is given by the formula:

[tex]K_p=K_c(RT)^{\Delta ng}[/tex]

Where,

[tex]K_p[/tex] = equilibrium constant in terms of partial pressure = ?

[tex]K_c[/tex] = equilibrium constant in terms of concentration = [tex]4.63\times 10^{-3}[/tex]

R = Gas constant = [tex]0.0821\text{ L atm }mol^{-1}K^{-1}[/tex]

T = temperature = [tex]527^oC=527+273=800K[/tex]

[tex]\Delta ng[/tex] = change in number of moles of gas particles = [tex]n_{products}-n_{reactants}=2-1=1[/tex]

Putting values in above equation, we get:

[tex]K_p=4.63\times 10^{-3}\times (0.0821\times 800)^{1}\\\\K_p=0.304[/tex]

The chemical reaction for the decomposition of phosgene follows the equation:

                   [tex]COCl_2(g)\rightleftharpoons CO(g)+Cl_2(g)[/tex]

At t = 0          0.760            0     0  

At [tex]t=t_{eq}[/tex]      0.760-x          x      x

The expression for [tex]K_p[/tex] for the given reaction follows:

[tex]K_p=\frac{p_{CO}\times p_{Cl_2}}{p_{COCl_2}}[/tex]

We are given:

[tex]K_p=0.304\\p_{COCl_2}=0.760-x\\p_{CO}=x\\p_{Cl_2}=x[/tex]

Putting values in above equation, we get:

[tex]0.304=\frac{x\times x}{0.760-x}\\\\x=0.352,-0.656[/tex]

Negative value of 'x' is neglected because partial pressure cannot be negative.

So, the partial pressure for the components at equilibrium are:

[tex]p_{COCl_2}=0.760-0.352=0.408atm\\\\p_{CO}=0.352atm\\\\p_{Cl_2}=0.352atm[/tex]

Hence, the partial pressure of the [tex]CO,Cl_2\text{ and }COCl_2[/tex] are 0.352 atm, 0.352 atm and 0.408 atm respectively.