Question

(a) What is the density of sulfur hexafluoride (MM = 146.1) gas at 703 torr and 30.6°C?
____g/L

(b) What is the molar mass of a vapor that has a density of 6.53 g/L at 13.7°C and 825 torr?
____ g/mol

Answer 1

(a) What is the density of sulfur hexafluoride (MM = 146.1) gas at 703 torr and 30.6°C?
____g/L

molar mass SF6 = 146.1 g/mol
p = 703/760=0.925 atm
T = 30.6 + 273 = 303.6 K

To calculate the density of sulfur hexafluoride use following expression:

d = P x MW / (R x T)

d = 0.925 x 146.1 / 0.08206 x 303.6

=5.42 g/L


(b) What is the molar mass of a vapor that has a density of 6.53 g/L at 13.7°C and 825 torr?

____ g/mol

T = 13.7 + 273 =286.7 K
p = 825 /760=1.086 atm

d = P x MW / (R x T)

MW = d(R x T) /P

molar mass = 6.53 x 0.08206 x 286.7 / 1.086

=141.46 g/mol