STP problem pressure

Question

A sample of Argon gas has a volume of 6.44 L at 55°C and 1.36 atm.

What would be the volume of this gas sample at STP ? L.

Answer 1

Two ways to solve this:

(1) Combined gas law; P1V1/T1 = P2V2/T2 and solving for V2, you have P1V1T2/P2T1 = V2. Plug in

P1=1.36 atm; V1=6.44 L; T1=328K; P2=1.00 atm; T2=273K (these are STP values).

(2) Ideal gas law: PV = nRT and solve for moles (n): n = PV/RT = (1.36 atm)(6.44 L)/(0.0821)(328K)

n = 0.325 moles of argon.

At STP 1 mole of ideal gas = 22.4 liters,

Volume at STP = 0.325 moles x 22.4 L/mole = 7.29 liters