Question

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?

Answer 1

Answer:

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