A 10.0-L flask containing He,1.00 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)6.00 mol
B)10.0 mol
C)10 .0 mol
D)119 mol

Question

Quizplus · Accepted Answer

Using Dalton's law of partial pressures, the partial pressure of He can be found by subtracting the partial pressures of Ar and Ne from the total pressure of the mixture:

PH = Ptotal - Par - Pne
PH = 24.5 atm - (1.00 mole/4.00 mole)(24.5 atm) - (3.00 mole/4.00 mole)(24.5 atm)
PH = 8.63 atm

Using the ideal gas law (PV = nRT) to solve for moles of He:

n = PV/RT = (8.63 atm)(10.0 L)/(0.0821 L atm/mol K)(298 K) = 0.342 mol

Therefore, there are 0.342 mol of He in the flask.

A 100-L Flask Containing He,1