Calculate the molar mass of a gas with a mass of 3.15 g, a pressure of 785 mmHg, and a temperature of 20 Celsius. The gas has a volume of 750 ml.

Molar mass = 105 g/mol

Explanation:

Given data:

Mass of gas = 3.15 g

Pressure = 785 mmHg

Temperature = 20°C

Volume of gas = 750 mL

Molar mass of gas = ?

Solution:

Pressure = 785 mmHg (785/760 = 1 atm)

Temperature = 20°C (20+273 = 293 K)

Volume of gas = 750 mL (750 mL× 1 L/1000 mL = 0.75 L)

PV = nRT

R = general gas constant (0.0821 atm.L/mol.K)

1 atm× 0.75 L =  n×0.0821 atm.L/mol.K × 293 K)

0.75 atm.L = n× 24.06 atm.L/mol

n = 0.75 atm.L / 24.06 atm.L/mol

n = 0.03 mol

Molar mass of gas:

Molar mass = Mass / number of moles

Molar mass = 3.15 g/ 0.03 mol

Molar mass = 105 g/mol