Question

A sample of oxygen gas at 20.0°C has a volume of 26.0L and exerts a pressure of 640.0mmHg. What is the mass of this gas?

Answer 1

$T = 20 + 273 = 293 \;K \\ V = 26.0 \;L \\ p = 640.0 \; mmHg = 0.8421 \;atm$

Ideal gas law

pV = nRT

R= 0.08206 L×atm/mol×K

$n = \frac{pV}{RT} \\ = \frac{0.8421 \times 26.0}{0.08206 \times 293} \\ = 0.91 \;mol \\ m = n \times M$

M(O₂) = 32 g/mol

$m = 0.91 \times 32 = 29.14 \;g$

Answer: 29.14 g