The Ideal Gas Law — Drills · Grade 11 Science

Chapter: States of Matter & Gases

What these drills covers

By the end of The Ideal Gas Law you should be able to:

I can use the ideal gas law PV = nRT to solve for pressure, volume, moles, or temperature, choosing the correct value of R.
I can calculate the molar volume of a gas at STP and use it to convert between moles and liters.

6 questions, multiple choice, numeric and written answer, each with a worked explanation.

Vocabulary used: ideal gas law, ideal gas constant (R), mole (n), STP, molar volume, Avogadro's Law, ideal gas.

Problem 1

Which equation is the ideal gas law?

PV = RT
PV = nRT
P = mV
V = nRT

Answer and explanation

PV = nRT

The ideal gas law is PV = nRT.

Problem 2

What volume does 2.0 mol of an ideal gas occupy at STP?

Answer and explanation

44.8 L

Volume = moles × 22.4 L/mol = 2.0 × 22.4 = 44.8 L.

Problem 3

How many moles of gas are in a 44.8 L sample at STP?

Answer and explanation

2 mol

Moles = volume ÷ 22.4 L/mol = 44.8 ÷ 22.4 = 2.0 mol.

Problem 4

Find the volume of 1.0 mol of gas at 2.0 atm and 546 K. (R = 0.0821 L·atm/mol·K)

Answer and explanation

22.4 L

V = nRT/P = (1.0 × 0.0821 × 546)/2.0 = 44.83/2.0 ≈ 22.4 L.

Problem 5

A 2.0 L flask contains gas at 4.0 atm and 250 K. How many moles are present? (R = 0.0821 L·atm/mol·K)

Answer and explanation

0.39 mol

n = PV/RT = (4.0 × 2.0)/(0.0821 × 250) = 8.0/20.525 ≈ 0.390 mol.

Problem 6

Why does one mole of any ideal gas occupy the same 22.4 L at STP, no matter which gas it is?

Answer and explanation

By Avogadro's Law, equal numbers of gas particles occupy equal volumes at the same temperature and pressure. The ideal gas law depends only on the number of moles (n), not on the type or mass of the gas, so one mole of any ideal gas fills 22.4 L at STP.

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