Help me please with the answer

Question

What is the molecular weight of a gas if 500 mL weighs 10 g at -23 °C and 380 torr?

unit:

Answer 1

PV = nRT Ideal Gas Law

P = pressure = 380 torr x 1 atm / 760 torr = 0.500 atm

V = volume = 500 ml = 0.500 L

n = moles of gas = ?

R = gas constant = 0.0821 Latm/Kmol

T = temperature = -23ºC + 273 = 250K

Solve for n...

n = PV/RT = (0.500 atm)(0.500 L) / (0.0821 Latm/Kmol)(250K)

n = 0.01218 moles of gas

Molecular weight = grams/moles = 10 g / 0.01218 moles

Molecular weight = 821 g / mole