Molar Mass

Related Examples and Practice Problems

A black-and-white worksheet titled "Molar Mass Practice Worksheet" with instructions to find molar masses of various chemical compounds, including NaBr, PbSO4, Ca(OH)2, Na3PO4, (NH2)2CO3, C6H12O6, and Fe3(PO4)2.
A worksheet titled 'Molar Mass Worksheet' with instructions to calculate molar masses of various chemicals, including Cl2, KOH, BeCl2, FeCl3, BF3, CCl2F2, Mg(OH)2, UF6, and SO2.
Molar Mass Worksheet with a list of chemical formulas for calculating molar masses.
A worksheet with two chemistry questions about molecular mass, written in black text on a white background.

Topic Summary & Highlights
and Help Videos

Core Concept

Molar mass is the mass of one mole of a substance. It is usually expressed in grams per mole (g/mol).

Practice Tips

  • Memorize Common Ions: Focus on learning the common polyatomic ions, charges, and patterns.

  • Roman Numerals for Transition Metals: Practice associating transition metals with their possible charges.

  • Cross-Method for Formulas: To determine the correct formula, use the “criss-cross” method to balance charges between cations and anions.

Topic Overview Podcast

Topic Related Resources

 LABORATORY 
 DEMONSTRATIONS 
 ACTIVITIES 
 VIRTUAL SIMULATIONS 

Core Concept

Molar mass is the mass of one mole of a substance. It is usually expressed in grams per mole (g/mol).

Calculating Molar Mass: 

To find a substance's molar mass, you add up the atomic masses of all the atoms in one of its molecules. Here's an example for calculating the molar mass of sulfuric acid (H2​SO4​).

The formula for sulfuric acid is H2​SO4​, which contains two hydrogen (H) atoms, one sulfur (S) atom, and four oxygen (O) atoms.

To find the total molar mass, follow these steps:

  1. Find the atomic masses of each element:

    • Hydrogen (H): 1.01 g/mol

    • Sulfur (S): 32.07 g/mol

    • Oxygen (O): 16.00 g/mol

  2. Multiply each atomic mass by the number of atoms in the formula:

    • Hydrogen: (1.01 g/mol) × 2 = 2.02 g/mol

    • Sulfur: (32.07 g/mol) × 1 = 32.07 g/mol

    • Oxygen: (16.00 g/mol) × 4 = 64.00 g/mol

  3. Add the results together to find the total molar mass:

    • Molar Mass of H2​SO4 ​ =2.02 g/mol + 32.07 g/mol + 64.00 g/mol = 98.09 g/mol

The molar mass of sulfuric acid (H2​SO4​) is 98.09 g/mol.

Core Concept

FYI - 

Molar Mass and Molecular Weight: Molar mass and molecular weight are often used interchangeably, but they are not exactly the same thing. Molecular weight is the sum of the atomic weights of all the atoms in a molecule, whereas molar mass is the mass of one mole of that molecule.

Molar Mass and Avogadro's Number: Avogadro's number is the number of particles in one mole of a substance (6.02 x 10^23). The molar mass of a substance is directly related to Avogadro's number, as one mole of any substance will always have a mass equal to its molar mass.

Brain Hack Tip

🧠 Here is a tip of how to remember how to remember how to name acids 🧠

Remember to “mole-tiply”

When converting to moles to grams using molar mass - you will multiply the moles by molar mass to get to grams.

Video Resources