Calculating Average Molecular Weight and Equilibrium Constants for Gas Mixtures

[tag16]

x + y = 1
92.011 x + 46.0055 y = 77.4395

x= -y + 1
92.011 (-y +1) + 46.0055 y = 77.4395
-92.011 y + 92.011 + 46.0055 y = 77.4395
-46.0055 y + 92.011= 77.4395
-46.0055 y = -14.5715
y = 0.316734
1- y = x
x = 0.683266

To find the degree of dissociation I did this:

n(N2O4)=77.4395/92=0.841 mol

degree dissociation: x(N2O4)/n(N2O4)= 0.683266/0.841= 0.812445= 81.24%


To find Kp I did:

n(N2O4)=77.4395/92=0.841 mol
n(NO2)= 77.4395/46=1.683 mol

Kp= n(N2O4)/(n(NO2))^2= 0.841/(1.683)^2= 0.296912

I think to find delta G standard I'd want to use this equation: delta G= -RTlnKp

and for delta S: delta S= delta G/T

Did I go about any of that right or is that not what I'm suppose to do?

 

[Borek]

y = 0.316734
1- y = x
x = 0.683266

Looks OK.

To find the degree of dissociation I did this:

n(N2O4)=77.4395/92=0.841 mol

degree dissociation: x(N2O4)/n(N2O4)= 0.683266/0.841= 0.812445= 81.24%

So you have calculated composition of the mixture only to ignore it now and not use the information in following calculations?

 

[tag16]

Is this right? If not I don't know how to find it.

PV = nRT --> n =PV/RT--> n = (1 − α)n + 2αn = PV/RT

α = (PV/nRT)− 1

 

[Borek]

n = (1 − α)n + 2αn

You have two different n in this equation - on the left, total number of moles after reaction took place, on the right - initial number of moles.

You know molar fractions of both gases present. Calculate numbers of moles of both. Use stoichiometry of the reaction to calculate initial number of moles of gas. Use definition of dissociation degree.