[Moose100]

SO3 decomposes on heating:
 2SO₂(g)  2SO₂(g) + O₂(g)
 A sample of pure SO3 was heated to a high temperature T. At equilibrium, the mole ratio of SO2 to
SO3 was 0.152 and the total pressure was 2.73 atm. If the piston was pushed in to cut the volume in half what is the new pressure?


Please *delete me*!  UI tried using the ratio to get the pressures on the left. 0.414 and 2.32 respectively.Also tried multiplying 2.73 by 2 but don't think this is the way.

Please help !! Thanks a million.

[billnotgatez]

SO3 decomposes on heating:
 2SO₂(g)  2SO₂(g) + O₂(g)
 A sample of pure SO3 was heated to a high temperature T. At equilibrium, the mole ratio of SO2 to
SO3 was 0.152 and the total pressure was 2.73 atm. If the piston was pushed in to cut the volume in half what is the new pressure?


Please *delete me*!  UI tried using the ratio to get the pressures on the left. 0.414 and 2.32 respectively.Also tried multiplying 2.73 by 2 but don't think this is the way.

Please help !! Thanks a million.

Do you have a typo in the formula you posted?

[Borek]

Trivial typo.

Many ways to skin that cat. Start by calculating K, you will need that. Then you can try to assume initial volume to be V and express initial number of moles of SO₃ in the initial mixture as a function of V. Next try to derive expression for the final pressure (new volume being V/2, and using K to find the new equilibrium) - you will find that V canceled out.

[Moose100]

Yes I did do the volume as V/2. Thanks I will be back later!

[Moose100]

Those concentrations I got ARE correct right?

[Borek]

Those concentrations I got ARE correct right?

Hard to tell not seeing them.

[Moose100]

I'm talking about the ones I posted earlier. I will put the new ones later. I'm thinking if those are wrong the new ones will be?

[mjc123]

If you mean 0.414 and 2.32 atm, that is wrong. 0.414 = 0.152*2.73, but 0.152 is the ratio of SO₂ to SO₃, not the ratio of SO₂ to total pressure.

[Moose100]

Right that is the ratio and I multiplied it by the beginning pressure to get 0.414 for S02 and 2.32 for Oxygen. I use these to get the constant. I wanted to ask before I put it down if this was the correct approach. Sorry if im being tedious.

[Enthalpy]

And is there any indication about what the temperature does when the piston is moved?

[Moose100]

Not at all they just say its really high.

[Borek]

Right that is the ratio and I multiplied it by the beginning pressure

And you were already told it is wrong - question clearly says what is the ratio of SO₂/SO₃, not what is the ratio ratio of SO₂/everything.

[Moose100]

OOps sorry. I will take a closer look here.

[Moose100]

Equilibrium conc of:

SO₃: 2.73-2x
SO₂: 2x
O₂  : x

2x/(2.73-2x)=0.152

x=0.180

Eventually I get to the point where K= 0.00415

Am I in the ballpark here?

[Moose100]

Ptotal=pO₂+pSO₃+pSO₂

pSO₂/pSO₃=0.152

pO₂/pSO₂= 0.5

Ptotal= 0.5pSO₂ +pSO₂/0.152 + pSO₂

Is this closer? I feel like everything I try is wrong.