Question

A 3.60 l gas sample is at a pressure of 95.5 kpa and a temperature of 25.0°c.if the gas sample weighs 6.10 g, calculate the molar mass of the gas.

Answer 1

Strategy of solution:

First, find the number of moles of the gas using the law pV = nRT. After that, find the molar mass by dividing the mass of the compound by the number of moles: molar mass = n / mm

Solution:

1)
p = 95.5 kPa
T = 25.0 + 273.15 K = 298.15 K
V = 3.60 l
R = 8.314 (l * kPa / K*mol)

=> n = pV / RT = [95.5 kPa * 3.60 l ] / [8.314 (l*kPa/K*mol) * 298.15 K] = 0.139 mol

2) mm = number of grams / number of moles = 6.10 g / 0.139 mol = 43.88 g/mol

Answer: 43.9 g / mol (rounded to three significant figures)