How to Convert Grams to Mols: 8 Steps (with Images)

Table of contents:

How to Convert Grams to Mols: 8 Steps (with Images)
How to Convert Grams to Mols: 8 Steps (with Images)

The mol is a standard unit of measurement in chemistry. It takes into account the different elements present in a chemical compound. Generally, the mass of compounds is given in grams and needs to be converted to moles. Although this is a simple calculation, there are some important steps that should be followed carefully. Use the method below to learn how to convert from grams to moles.


Part 1 of 2: Molecular mass

Convert Grams to Moles Step 1

Step 1. Gather the tools needed to solve a chemistry problem

Having everything you need easily at hand will simplify the problem solving process. You will need the following tools:

  • Pencil and paper. It will be much easier to solve the calculations by writing them down on paper. Remember to write down all the steps so you don't miss any points on your exercise or test.
  • A periodic table. You will need to determine the atomic mass of the elements from the table.
  • A calculator. It will help simplify calculations with more complex numbers.
Convert Grams to Moles Step 2

Step 2. Identify the elements of the compound that you need to convert to mols

The first step in calculating molecular mass is to identify each element present in the chemical compound in question. It's easy to distinguish the elements because their symbols (that is, the abbreviations) are only one or two letters long.

  • If the symbol of an element is written with two letters, the first will be uppercase and the second will be lowercase. For example, Mg is the abbreviation for the element magnesium.
  • The NaHCO compound 3 it has four different elements: sodium (Na), hydrogen (H), carbon (C) and oxygen (O).
Convert Grams to Moles Step 3

Step 3. Determine the number of atoms of each element in the compound

You need to know how many atoms of each element are present in the compound in order to calculate its molecular mass. The number of atoms of each element can be found at the bottom right of the symbol.

  • For example, compound H 2 O has two hydrogen atoms and one oxygen atom.
  • If a compound has parentheses followed by a subscript number, each element within the parentheses must be multiplied by that number. For example, the compound (NH 4)2 S has two N atoms, eight H atoms and one S atom.
Convert Grams to Moles Step 4

Step 4. Write the atomic mass of each of the elements

Using the periodic table will be the easiest way to find the atomic mass of an element. Locate the element in the table: the atomic mass will usually be at the bottom of its symbol.

For example, the atomic mass of oxygen is approximately 15, 99

2780559 5

Step 5. Calculate the molecular mass

The molecular mass of a substance is calculated by adding the number of atoms of each element multiplied by the atomic mass of the element. It is necessary first to know the molecular mass of the compound and then convert it from grams to moles.

  • Multiply the number of atoms of each element appearing in the compound by its atomic mass.
  • Add the total mass of each element in the composite.
  • For example, the molecular mass of the compound (NH 4)2 S will be (2 x 14, 01) + (8 x 1,01) + (1 x 32, 07) = 68, 17 g/mol.
  • Molecular mass can also be called molar mass.

Part 2 of 2: Converting Grass to Mols

2780559 6

Step 1. Assemble the conversion formula

The number of moles you have in a compound can be calculated by dividing the number of grams of that compound by its molecular mass.

  • The formula will be mols = mass in grams of the compound/mole mass of the compound.
2780559 7

Step 2. Substitute the values ​​in the formula

After you've built the formula, the next step is to put the values ​​in the correct places. An easy way to check that everything is in the right place is to look at the measurement units. After canceling all units, only mols should remain.

2780559 8

Step 3. Solve the equation

Using a calculator, divide the mass in grams by the molar mass. The result of this division will be the number of moles in the element or compound.

  • For example, suppose you have the mass of 2 g of water, that is, H 2 O, and want to convert it to mols. The molecular mass of compound H 2 O is 18 g/mol. Dividing 2 by 18 gives approximately 0.11 moles of H 2 O.


  • Always include the element or compound name with the answer.
  • If your exercise question or chemistry exam asks you to show your calculations, remember to clearly identify the final answer by drawing a circle or rectangle around it.

Popular by topic