1. A mixture of He, Ar, and Xe has a total pressure of 2.10 atm . The partial pr
ID: 514046 • Letter: 1
Question
1. A mixture of He, Ar, and Xe has a total pressure of 2.10 atm . The partial pressure of He is 0.400 atm , and the partial pressure of Ar is 0.350 atm . What is the partial pressure of Xe? Express your answer to three significant figures and include the appropriate units.
2. A volume of 18.0 L contains a mixture of 0.250 mole N2 , 0.250 mole O2 , and an unknown quantity of He. The temperature of the mixture is 0 C , and the total pressure is 1.00 atm . How many grams of helium are present in the gas mixture? Express your answer to three significant figures and include the appropriate units.
Explanation / Answer
1. PHe = 0.4atm
PAr = 0.35atm
PHe + PAr + PXe = 2.1atm
0.4 + 0.35 + PXe = 2.1
0.75 + PXe = 2.1
PXe = 2.1-0.75 = 1.35atm
2. PV = nRT
n = PV/RT
= 1*18/0.0821*273 = 0.8 moles
nN2 + nO2 + nHe = 0.8
0.25 + 0.25 + nHe = 0.8
nHe = 0.8-0.5 = 0.3moles
mass of He = no of moles * gram atomic mass
= 0.3*4 = 1.2g
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