A gaseous product has a mass of 2.34 g and occupies a volume of 0.854 L. The temperature in the laboratory is 302 K, and the air pressure is 1.04 atm. Calculate the molar mass of the gas.

22.4 g/mol

44.0 g/mol

65.3 g/mol

86.9 g/mol

The right choice is (C) 65.3 g/mol

Explanation:

According to the ideal gas equation

PV = nRT

we have the n as the number of moles. Since we know that

moles = mass / molar mass

Mass is given to us as 2.34 g so arranging the above equation

PV = (mass/molar mass) RT

Putting the values

Molar mass = (mass) RT / (PV)

= (2.34 g) (0.082 (302) / (1.04) (0.854)

= 65.244 g/mol. OR approximately 65.3 g/mol.

65.3 g/mol.

Explanation:

We can use the genral gas law of ideal gases:

PV = nRT,

where, P is the pressure of the gaseous compound in atm (P = 1.04 atm).

V is the volume of the gaseous compound in L (V = 0.854 L).

n is the no. of moles of the gaseous compound in mol.

R is the general gas constant (R = 0.082 L. atm/mol. K).

T is the temperature of the gaseous compound in K (T = 302 K).

∵ n = mass/molar mass.

∴ PV = (mass/molar mass) RT.

∴ Molar mass = (mass) RT / (PV) = (2.34 g) (0.082 L. atm/mol. K) (302 K) / (1.04 atm) (0.854 L) = 65.244 g/mol. ≅ 65.3 g/mol.