Question

14.A 4.25 gram sample of an unknown gas is found to occupy a volume of 1.70 L at a pressure of 883 mm Hg and a temperature of 58 °C. The molar mass of the unknown gas is ______
g/mol.

Answer 1

Answer:

58.5g/mol

Explanation:

Given parameters:

Mass of gas  = 4.25g

Volume  = 1.7L

Pressure  = 883mmHg

                760mmHg  = 1 atm

                883mmHg  = $\frac{883}{760}$   = 1.16atm

Temperature  = 58°C  = 58 + 273  = 331K

Unknown:

Molar mass of sample  = ?

Solution:

To solve this problem, we use the ideal gas equation to find the number of moles;

            PV  = nRT

 P is the pressure

V is the volume

n is the number of moles

R is the gas constant  = 0.082atmdm³mol⁻¹K⁻¹

 T is the temperature

           n  = $\frac{PV}{RT}$   = $\frac{1.16 x 1.7}{0.082 x 331}$   = 0.07mole

 Since;

            mass  = number of moles x molar mass

            4.25  = 0.07 x molar mass

 Molar mass  = 58.5g/mol