What is the molar mass of a sample of gas that has the density of 1.55g/L at 1.45 atm pressure and 25.0°C?

Answer 1

Assume we have 1 liter of the unknown gas. The mass of this would be 1.55 g.

Assume the unknown gas behaves as an ideal gas.

Use the ideal gas law to calculate moles of the unknown gas.

PV = nRT

P = pressure = 1.45 atm

V = volume = 1 L

n = moles of gas = ?

R = gas constant = 0.0821 Latm/Kmol

T = temperature in Kelvin = 25 + 273 = 298K

Solve for n (moles):

n = PV/RT

n = (1.45)(1) / (0.0821)(298)

n = 0.0593 moles

Molar mass = grams / moles

Molar mass = 1.55 g / 0.0593 moles

Molar mass = 26.1 g / mole