Molar Mass Calculations Worksheet

Molar Mass Calculations Worksheet

Welcome to our molar mass calculations worksheet! Molar mass is a crucial concept in chemistry that measures the mass of a given substance in grams per mole. By knowing the molar mass of a substance, we can easily determine the number of moles present in a given amount of that substance. This worksheet will help you practice calculating the molar mass of various compounds and elements, as well as applying that knowledge to solve problems involving moles and mass in chemical reactions.

What is Molar Mass?

Molar mass is the mass of a given substance expressed in grams per mole. It is calculated by summing the atomic masses of all the elements in a chemical formula. The unit for molar mass is grams per mole (g/mol). For example, the molar mass of water (H2O) is 18.015 g/mol, which is the sum of the atomic masses of two hydrogen atoms (1.008 g/mol each) and one oxygen atom (16.00 g/mol). Molar mass is a fundamental concept in chemistry that enables us to convert between mass and moles in chemical reactions.

Molar Mass Calculations Worksheet

Calculating Molar Mass

To calculate the molar mass of a compound, follow these steps:

  1. Write down the chemical formula of the compound.
  2. Determine the atomic mass of each element in the compound from the periodic table.
  3. Multiply the atomic mass of each element by the number of atoms of that element in the compound.
  4. Sum up the products from step 3 to get the molar mass of the compound.

For example, let’s calculate the molar mass of carbon dioxide (CO2):

  • Atomic mass of carbon (C) = 12.011 g/mol
  • Atomic mass of oxygen (O) = 15.999 g/mol
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Molar mass of CO2 = (1 x 12.011 g/mol) + (2 x 15.999 g/mol) = 44.01 g/mol

Applying Molar Mass in Chemical Reactions

Once you have calculated the molar mass of a substance, you can use it to convert between mass and moles in chemical reactions. This allows you to determine the amount of reactants needed or products formed in a reaction. The following equation summarizes the relationship between mass, moles, and molar mass:

n = m/M


  • n = number of moles
  • m = mass of the substance (in grams)
  • M = molar mass of the substance (in g/mol)

By rearranging this equation, you can calculate the mass or molar mass of a substance when given the number of moles. This is especially useful in stoichiometry, where the mole ratio of reactants and products in a chemical reaction is used to determine the quantities of substances involved.

Practice Worksheet

Now that you have a basic understanding of molar mass calculations, it’s time to put your knowledge to the test with the following practice problems:

  1. Calculate the molar mass of magnesium sulfate (MgSO4).
  2. How many moles are present in 25.0 grams of calcium chloride (CaCl2)?
  3. If 4.50 moles of sulfuric acid (H2SO4) are reacted with excess magnesium, how many grams of magnesium sulfate (MgSO4) are formed?

Take your time to work through each problem and check your answers using a periodic table. If you need more practice, feel free to create your own molar mass calculations and stoichiometry problems. The more you practice, the better you will become at applying these concepts in chemistry.


Understanding molar mass and its applications in chemical reactions is essential for success in chemistry. By mastering molar mass calculations, you can effectively analyze and predict the outcomes of chemical reactions. This worksheet serves as a valuable tool for practicing molar mass calculations and applying them in stoichiometry problems. We hope you found this worksheet helpful and that you continue to strengthen your skills in chemistry.