Question

What is the molecular weight of a pure gaseous compound having a density of 4.95 g/L at -35°C and 1020 torr? 120 g/mol 44 g/mol 11 g/mol 72 g/mol 24 g/mol

Answer 1

P= 1020.0 torr

= (1020.0/760) atm

= 1.3421 atm

T= -35.0 oC

= (-35.0+273) K

= 238 K

density = 4.95 g/L

Lets derive the equation to be used

use:

p*V=n*R*T

p*V=(mass/molar mass)*R*T

p*molar mass=(mass/V)*R*T

p*molar mass=density*R*T

Put Values:

1.3421 atm * MM = 4.95g/L * 0.08206 atm.L/mol.K *238.0 K

MM = 72.0 g/mol

Answer: 72 g/mol