# Attn: DrBob222

posted by .

A .326L container holds 0.146g of Ne and an unknown amount of Ar at 30C and the total pressure is 627 mmHg. Calculate the moles of Ar present?
(I have calculated temp 308K, pressure is 0.825 atm and moles of Ne are .007)

Chem - DrBob222, Wednesday, March 3, 2010 at 3:25pm
T is 303 and not 308 K which means you need to recalculate pressure and n for Ne.
Use PV = nRT
You can calculate moles Ne, plug that in for n, and plug in R, T, and V. Calculate pressure for Ne (I get something like 0.55 atm but I rounded here and there. That will be in atm so change to mm Hg. You know total pressure is 627 mm Hg, subtract pressure Ne to obtain pressure Ar, then plug that back into PV = nRT to calculate n for Ar. Remember to convert mmHg back to atm.

Dr. Bob,

I'm calculating moles of Ar to be 0.0038, however, when plugging this into the online homework program it's marking it as incorrect. Am I doing a step incorrectly or do you get a similar answer? Thanks!

• Attn: DrBob222 -

I get a similar answer but not the same. I obtained 0.00358 moles Ar.