What is the density and molar mass of the gas?

Question

A 1.55g sample of an unknown gas at 69°C and 1.10 atm is stored in a 1.55 L flask.

What is the density of the gas? (g/L

What is the molar mass of the gas? (g/mol)

Answer 1

Use the ideal gas law;

PV = nRT

P = pressure =1.10 atm

V = volume = 1.55 L

n = moles = ?

R = gas constant = 0.0821 Latm/Kmol

T = temperature in Kelvin = 69ç + 273 = 342K

Solving for n (moles), we have...

n = PV/RT = (1.10)(1.55) / (0.0821)(342)

n = 0.0607 mols of unknown gas

Density = mass / volume = 1.55 g / 1.55 L = 1.00 g / L

Molar mass = grams / moles = 1.55 g / 0.0607 moles = 25.5 g/mol