Question

A chemist isolated a gas in a glass bulb with a volume of 254 mL at a temperature of 28 °C and a pressure (in the bulb) of 12 torr. The gas weighed 15.2 mg. What is the molar mass of this gas?

Answer 1

we have:

P = 12.0 torr

= (12.0/760) atm

= 0.0158 atm

V = 254.0 mL

= (254.0/1000) L

= 0.254 L

T = 28.0 oC

= (28.0+273) K

= 301 K

find number of moles using:

P * V = n*R*T

0.0158 atm * 0.254 L = n * 0.0821 atm.L/mol.K * 301 K

n = 1.623*10^-4 mol

mass of solute = 15.2 mg

= 0.0152 g [using conversion 1 g = 1000 mg]

we have below equation to be used:

number of mol = mass / molar mass

1.623*10^-4 mol = (0.0152 g)/molar mass

molar mass = 93.66 g/mol

Answer: 93.7 g/mol