[jay11245]

DATA
0 °C = 273.2 K
Molar Masses:
• SO2: 64.07 g/mol
• SO3: 80.07 g/mol


An evacuated vessel of volume 789.1 mL has a mass of 32.301 g.
A mixture of SO2 and SO3 was introduced into the vessel at a total pressure of 1.41 atm and a temperature of 35.0 °C. The mass of the container and its contents was found to be 35.283 g.

ive tried to find the average molar mass and mole fraction from this but am really struggling

any help with calcs would be appreciated

[Hunter2]

m1 + m2 = mtot. mtot = (mVessel + gas) - m(vessel)
n1+n2 = n(tot), n( tot) = p*V/RT
n= m/M

Enough equations to solve.

[jay11245]

m1 + m2 = mtot. mtot = (mVessel + gas) - m(vessel)
n1+n2 = n(tot), n( tot) = p*V/RT
n= m/M

Enough equations to solve.

This helped heaps thank you!!!
This is my working out in case I made a mistake
mtotal = 35.283-32.301 = 2.982
Ntotal = PV/RT = 1.41x0.7891/0.08206x(273.2+35)
ntotal = 0.04368134

.: average Molar mass 2.982/0.04368134

[Hunter2]

So far so good, We want to know the mole Fraction or in other works how much mole SO2 and SO3 is in the mixture by mole

n1/(n1+n2) and n2/(n1+n2)

Can also calculate the masses.

[jay11245]

So far so good, We want to know the mole Fraction or in other works how much mole SO2 and SO3 is in the mixture by mole

n1/(n1+n2) and n2/(n1+n2)

Can also calculate the masses.

So i think to do i believe I would take the average molar Mass (M) than the Molar masses of SO3 and SO2 and do (M - mSO3) / (mSO2 - mSO3) and then that would give me the molar ratio of SO2.

Again thank you so much for the help this has stumped me for a few days!

[Hunter2]

No. Molar Mass unit is g/mol and mass is g. Dont mix units.

You have n(tot.) = n1 + n2 express n1 and n2 as mass m1 and m2.
You have m1 + m2 = m(tot)

You have two equations with two variables. Solve for m1 and m2 , then convert to n1 and n2.

[jay11245]

No. Molar Mass unit is g/mol and mass is g. Dont mix units.

You have n(tot.) = n1 + n2 express n1 and n2 as mass m1 and m2.
You have m1 + m2 = m(tot)

You have two equations with two variables. Solve for m1 and m2 , then convert to n1 and n2.

Sorry i must've confused you with my explanation cause i got the answer right - ill break down my working for you

(the value of the vessel is different fyi)

n total = (1.41x0.7888) / (0.08206 x 308.2)
n total = 0.043976622
m total = 35.283 - 32.301
m total = 2.982

Molar mass average = 2.982/0.043976622
= 67.8

Molar ratio = (Average Molar Mass - Molar mass of SO3) / (Molar Mass of SO2 - Molar Mass of SO3)
= (67.8 - 80.07) / (64.07 - 80.07)
 = 0.767

This gave me the right answer (with a sig fig error which was waived)

I wouldnt have been able to do it without you so thank you

[Hunter2]

Well but it doesn't says how many moles or g of SO2 and SO3 is in the mixture.

n(tot) = n1 + n2
Using  n = m/M
n(tot) = m1/M1 + m2/M2

And m(tot) = m1 + m2

Solve for m1 and m2