Chemistry - Ideal gas equation question

1. Nov 12, 2007

david18

A steel gas bottle contains 4500g of oxygen. The pressure of the gas inside the bottle is 6492Pa. If 700g of gas are slowly released from the bottle, what will be the new pressure of the remaining gas? (Assume that the temperature stays constant when the oxygen is released)

I'm having trouble with this question as I can only find PV but not P on its own.

Thanks

2. Nov 12, 2007

mgb_phys

Use PV = nRT before and after the release.
You know the change in 'n' the number of moles, and V stays the same, volume of bottle doesn't change.

3. Nov 20, 2007

MichaelXY

Would you take the Pa/mol and multiply that by the final mol. I get 5429 Pa. I am learning this subject as well, so I am curious.

4. Nov 20, 2007

mgb_phys

PV = nRT
V is constant, T is constant, R is constant (obviously!) so all you need is P/n before and after. YOu can work in totally arbitrary units for n since we are cancelling thme out

P1/n1 = P2/n2
P2 = P1 n2/n1 = 6492 * (4500-700)/4500 = 5482 Pa