Question

An empty glass bulb has a volume of 350. mL and a mass of 82.561g.

When filled with an unknown gas at 733 mmHg and 22 deg. C, the

bulb has a mass of 82.786g. Is the gas argon, methane or nitrogen    monoxide?

Answer 1

The mass of the unknown gas = (82.786 – 82.561)g = 0.225 g

Volume the gas was occupied = 350 ml = 0.350 Liter, pressure, P = 733 mmHg = 733/760 atm., and temperature

= 22^oC = (273+22) K = 295 K.

The relationship is, PV = nRT, we need to find out the n, number of moles, so that we can find out the M.Wt of the unkonw gas.

R=0.082 L-atm/K/mol

n = PV/RT = (733/760)*0.350/(0.082*295) mols = 0.01395 mols.

Now, 0.01395 moles = 0.225 g

so, 1 mole = 0.225/0.01395 g =16.13 g

Therefore, the molar mass is 16.13 g/mol, the gas is Methane, CH₄