Question

Determine the molar mass of freon–11 gas if a sample weighing 0.597 g occupies 100. cm3 at 95°c, and 1,000. mmhg (r = 0.08206 l • atm/k • mol, 1 atm = 760 mmhg).

Answer 1

We can first find the number of moles using the ideal gas law equation,
PV = nrT
where P - pressure - 1000 mmHg / 760 mmHg/atm = 1.32 atm 
V - volume -  100 x 10⁻³ L
n - number of moles 
r - universal gas constant - 0.08206 LatmK⁻¹mol⁻¹
T - temperature in Kelvin - 95 °C + 273 = 368 K
substituting these values 
1.32 atm x 100 x 10⁻³ L = n x 0.08206 LatmK⁻¹mol⁻¹ x 368 K
n = 0.00437 mol

molar mass can be determined as follows
molar mass = mass present / number of moles 
molar mass = 0.597 g / 0.00437 mol = 136.6 g/mol
molar mass of gas is 137 g/mol