sample of a gas weighs 3.05 g and has a volume of 896.0 mL at 945.0 torr and 31.0 °C. What is its molar mass?

Molar mass is 68.4 g/mol

Explanation:

Let's apply the Ideal Gases Law to solve this:

P. V = n. R. T

P is pressure (atm)

V is volume (L)

n, the number of moles

R, 0.082 L. atm/mol. K

T is absolute T° → T° K = T°C + 273

Let's make the conversion.

896 mL. 1 L/1000 mL = 0.896 L

945 Torr. 1 atm / 760 Torr = 1.24 atm

T° K = 31°C + 273 → 304 K

Now we replace in the formula, to determine the moles

1.24 atm. 0.896 L = n. 0.082 L. atm/mol. K. 304K

(1.24 atm. 0.896 L) / (0.082 L. atm/mol. K. 304K) = n

0.0445 mol = n

Molar mass is g / mol → 3.05 g / 0.0445 mol = 68.4 g/mol