A 22.4 liter sample of gas at stp weighs 12.0 grams. What is the molecular weight of the gas

12g/mol

Explanation:

At STP, the value of temperature and pressure is 273.15K and 1.0atm respectively.

Data

T = 273.15

P = 1.0 atm

V = 22.0L

m = 12.0g

R = 0.082L.atm / mol.K

From ideal gas equation,

PV = nRT

But n = number of moles = mass (m) / molar mass (M)

n = m / M

PV = mRT/ M

M = mRT / PV

M = (12.0 * 0.082 * 273.15) / (1.0 * 22.4)

M = 268.7796 / 22.4

M = 11.999g = 12g/mol

The molar mass of the gas is 12g/mol