[Bysons]

What is the total pressure, in atm, in a vessel containing 3.0 mole of Kr, 4.0 mole of Xe, and 0.5 mole of H2, and in which the partial pressure of Kr is 0.84 atm?

I know to get total pressure you add each partial pressure and to find partial pressure you times the total by the mole ratio. However I am unsure of finding total pressure when given only one partial pressure and no volumes.

[curiouscat]

to find partial pressure you times the total by the mole ratio

That's what you use here. Do it for Kr

[Bysons]

I divided 0.84 by 0.25(3/12), but that answer is incorrect.

[Borek]

How many moles in total?

3 moles - 0.84 atm

total moles - x atm

Do you see where it comes from?

[curiouscat]

3.0 mole of Kr, 4.0 mole of Xe, and 0.5 mole of H2

[Big-Daddy]

Find the ratio of total moles to moles of Kr and this is taken to be the same as the ratio of total pressure to Kr's partial pressure. So once you've found the first ratio you can easily find the total pressure just by multiplying out by Kr's partial pressure. Ask back if it's still not clear.