What is the molar mass of a gas if 12.0 L of the gas at STP has a mass of 16.0 grams?

Question

Quizplus · Accepted Answer

We can use the ideal gas law to solve this problem:

PV = nRT

At STP (Standard Temperature and Pressure), P = 1 atm and T = 273 K.

The volume of the gas is given as 12.0 L, which we can convert to 0.012 m^3.

We can rearrange the equation to solve for the number of moles of gas:

n = PV/RT = (1 atm)(0.012 m^3)/(0.0821 L*atm/mol*K)(273 K) ≈ 0.00046 mol

The molar mass is then:

molar mass = mass/n = 16.0 g/0.00046 mol ≈ 34.8 g/mol

Therefore, the best choice is D, 29.9 g, which is the closest to our calculated molar mass.

What Is the Molar Mass of a Gas If 12