How to Calculate Molar Mass

Step-by-Step Guide

1. 1

   Step 1: Understand molar mass.

   Molar mass is the mass (in grams) of one mole of a substance.Using the atomic mass of an element and multiplying it by the conversion factor grams per mole (g/mol), you can calculate the molar mass of that element.
2. 2

   Step 2: Find the relative atomic mass of the element.

   An element's relative atomic mass is the average mass, in atomic units, of a sample of all its isotopes.This information can be found on the periodic table of elements.
   
   Locate the element and find the number underneath the symbol for the element.
   
   It will not be a whole number, but will have decimals.
   
   For example, for hydrogen, the relative atomic mass is
   1.007; for carbon, it is
   12.0107; for oxygen, it is
   15.9994; and for chlorine, it is
   35.453. , This is defined as
   0.001 kilogram per mole, or 1 gram per mole.
   
   This converts atomic units to grams per mole, making the molar mass of hydrogen
   1.007 grams per mole, of carbon
   12.0107 grams per mole, of oxygen
   15.9994 grams per mole, and of chlorine
   35.453 grams per mole.
   
   Some elements are only found in molecules of 2 atoms or more.
   
   This means that if you want to find the molar mass of elements that are composed of 2 atoms, such as hydrogen, oxygen, and chlorine, then you'll have to find their relative atomic masses, multiply them by the molar mass constant, and then multiply the result by
   2.
   
   For H2:
   1.007 x 2 =
   2.014 grams per mole; for O2:
   15.9994 x 2 =
   31.9988 grams per mole; and for Cl2:
   35.453 x 2 =
   70.096 grams per mole.
3. 3

   Step 3: Multiply the relative atomic mass by the molar mass constant.

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