Practice Molar Mass in Chemistry

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

The mass in grams of exactly one mole of a substance, calculated by summing the atomic masses of all atoms in the chemical formula.

How much one mole weighs. For elements, it's the number on the periodic table.

Showing a random 20 of 50 problems.

Example 1

challenge
100ย g100\text{ g} of an oxide MOMO contains 0.50.5 mol. If O=16, what is the atomic mass of M?

Example 2

medium
What is the molar mass of Ca(OH)2Ca(OH)_2? (Ca=40, O=16, H=1)

Example 3

easy
What is the molar mass of CO2CO_2? (C=12, O=16)

Example 4

easy
How many moles are in 50โ€‰g50\,\text{g} of CaCO3\text{CaCO}_3? (M=100โ€‰g/molM = 100\,\text{g/mol})

Example 5

medium
How many grams of CO2CO_2 are in 0.5 mol? (M=44M=44)

Example 6

hard
A compound has formula X2O3\text{X}_2\text{O}_3 with molar mass 102โ€‰g/mol102\,\text{g/mol}. (O = 16) Find the atomic mass of X.

Example 7

hard
Calculate the molar mass of hydrated copper sulfate CuSO4โ‹…5H2O\text{CuSO}_4 \cdot 5\text{H}_2\text{O}. (Cu = 63.5, S = 32, O = 16, H = 1)

Example 8

medium
What is the molar mass of H2SO4H_2SO_4? (H=1, S=32, O=16)

Example 9

easy
Calculate the molar mass of glucose (C6H12O6\text{C}_6\text{H}_{12}\text{O}_6).

Example 10

hard
How many grams of oxygen are in 98โ€‰g98\,\text{g} of H2SO4\text{H}_2\text{SO}_4? (M=98M = 98, O = 16)

Example 11

easy
What is the molar mass of MgO\text{MgO}? (Mg = 24.3, O = 16.0)

Example 12

hard
0.500โ€‰mol0.500\,\text{mol} of an unknown gas weighs 22.0โ€‰g22.0\,\text{g}. Identify the gas if it is a common diatomic.

Example 13

easy
What is the molar mass of NaClNaCl? (Na=23, Cl=35.5)

Example 14

easy
What is the molar mass of O2O_2? (O=16)

Example 15

easy
What is the molar mass of water H2OH_2O? (H=1, O=16)

Example 16

easy
Calculate the molar mass of sulfuric acid (H2SO4\text{H}_2\text{SO}_4). (H = 1.008, S = 32.07, O = 16.00)

Example 17

challenge
A compound is 2 mol and 36ย g36\text{ g}. If it contains only H and O in a 2:1 atom ratio, what is it?

Example 18

hard
What mass of KClO3\text{KClO}_3 contains 48โ€‰g48\,\text{g} of oxygen? (K = 39, Cl = 35.5, O = 16)

Example 19

easy
How many moles are in 58.5ย g58.5\text{ g} of NaClNaCl? (M=58.5M = 58.5)

Example 20

medium
What is the molar mass of (NH4)2SO4(NH_4)_2SO_4? (N=14, H=1, S=32, O=16)