# Homework Help: What is the degree of dissociation?

1. Sep 17, 2010

### zorro

1. The problem statement, all variables and given/known data

At 627 C and 1 atm pressure, SO3 partially dissociated into SO2 and O2 by SO3--->SO2 +1/2O2. The density of equilibrium mixture is 0.925g/L. What is the degree of dissociation?

2. Relevant equations

3. The attempt at a solution

I found out the average molecular weight of the mixture by the formula PM=DRT
where D is the density.

Then, average molecular weight = sum of product of mole fractions and molar mass
moles at equilibrium-
SO3- 1-x
SO2- x
O2- x/2

But I did not get correct answer.
The answer is 0.34
Please provide a detailed explanation

2. Sep 17, 2010

### Staff: Mentor

Show more details of your work.

3. Sep 17, 2010

### zorro

M= DRT/P
M=0.925 x 0.0821 x 900/1= 68.3

this average molecular weight = [80(1-x) + 64x + 32(x/2)] / (1+x/2)
solving this I am getting absurd answer.

4. Sep 17, 2010

### Staff: Mentor

Check your math.

5. Sep 18, 2010

### zorro

I checked it again. But no error in math. I guess some equations are wrong.

6. Sep 18, 2010

### Staff: Mentor

Check your check then, I have solved your equation and got the correct answer.

Last edited by a moderator: Aug 13, 2013
7. Sep 18, 2010

### zorro

Oh yes. Thanks alot.

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