A 10.0-L flask containing He,2.00 mole of Ar,and 3.00 mole of Ne has a total pressure of 24.5 atm at 25°C.How many moles of He are in the flask?
A)5)00 mol
B)10.0 mol
C)114 mol
D)119 mol

Question

Quizplus · Accepted Answer

First, we need to use the Ideal Gas Law to find the total number of moles in the flask:
PV = nRT
n = PV/RT
n = (24.5 atm)(10.0 L)/(0.0821 L·atm/mol·K)(298 K)
n = 100.8 mol
Next, we can subtract the moles of Ar and Ne to find the moles of He:
n(He) = total moles - moles of Ar - moles of Ne
n(He) = 100.8 mol - 2.00 mol - 3.00 mol
n(He) = 95.8 mol 
Therefore, there are 5.00 moles of He in the flask.

A 100-L Flask Containing He,2