Question

What is the molar mass of a gas which has a density of 0.00249 g/mL at 20.0 degrees celcius and 744.0 mm Hg?

Answer 1

61.24 is the molar mass of a gas which has a density of 0.00249 g/mL at 20.0 degrees celcius and 744.0 mm Hg.

Explanation:

given that:

density = 0.00249 g/ml ($\frac{mass}{volume}$)  or 2.49 grams/litre

P = 744 mm Hg OR 0.978 atm

T = 20 Degrees or 293.15 Kelvin

R = 0.08206 Litre atm/mole K

molar mass =?

Formula used/

PV = nRT    equation 1

here n is number of moles:

n = $\frac{mass}{atomic mass}$

putting the value of n and value of density in the equation 1:

PV = $\frac{mass}{molar mass}$ x RT

molar mass = $\frac{mass}{volume}$ x $\frac{RT}{P}$

                    = density x $\frac{RT}{P}$

                     = $\frac{2.49 x 0.08276 x 293.15}{0.978}$

                     = 61.24 is the molar mass of the gas.