In chemistry, the mole is a fundamental (SI) unit used to measure the amount of a substance. It is sometimes referred to as the chemical amount. A mole ratio is ​a ratio between the amounts in moles of any two compounds involved in a chemical reaction.

A mole contains 6.023 x 1023 units. These units can be atoms, molecules, ions, or anything else.

concept of mole


  • 1 mole of sulfur atom = 6.023 x 1023 sulfur atoms
  • 1 mole of oxygen molecule = 6.023 x 1023 oxygen molecules.
  • 1 mole of sodium ions = 6.023 x 1023 sodium ions

Read about Molarity here:

What is a Mole Ratio?

A mole ratio is ​a ratio between the amounts in moles of any two compounds involved in a chemical reaction. It is used as a conversion factor between the reactants and the products. The mole ratio is calculated in the balanced equation only. Calculations can be made to predict how much product can be obtained from a given number of moles of reactant

A mole ratio is a dimensionless unit. Because it produces mole: mole, units of moles are canceled out

In order to determine the molar ratio between any two elements or compounds in a chemical reaction, you have to follow these steps.

  1. Balance the chemical reaction.
  2. Obtain the coefficients of the corresponding elements or compounds in the balanced equation.
  3. Calculate the ratio between these coefficients.


water equation
  • Here the coefficients of H2 =2
  • The coefficients of O2 = 1
  • The coefficients of H2O = 2

In this chemical equation, 1 mole of Oxygen (O2) reacts with 2 moles of hydrogen (H2) to produce 2 moles of water (H2O).

To determine the mole ratio of any two components of the equation, compare the coefficients of each component in the equation.

  • Mole ratio between H2 and O2 = (2 mole of H2 / 1 mole of O2) = 2:1
  • Mole ratio between H2 and H2O = (2 mole of H2 / 2 mole of H2O) = 2:2
  • Mole ratio between O2 and H2O = (1 mole of O2 / 2 mole of H2O) = 1:2

How many moles of H2 molecules will react with 0.27 moles of O2 molecules in the given equation?

equation 2

So the number of moles of H2= 0.27 × 2 = 0.54 mole.

Concepts Berg

What is the molar ratio between sodium and chlorine in the formation of table salt?

2 Na + Cl→   2 NaCl

The ratio of moles of Na to moles of Cl2 is 2:1.

How to calculate the molar ratio from molecular weight?

To determine the molar ratio from the molecular weight, you need the mass of each substance, then:
  1. Convert the molecular weight of the first substance into its molar mass.
  2. Divide the mass of the first substance by its molar mass to obtain the number of moles used (or produced) in the reaction.

What is the mole ratio for the production of ammonia?

N2 (g) + 3H2 (g)   →    2NH3 (g)

  • Mole ratio between H2 and N2 = (3 mole of H2 / 1 mole of N2) = 3:1
  • Mole ratio between H2 and NH3 = (3 mole of H2 / 2 mole of NH3) = 3:2
  • Mole ratio between N2 and NH3 = (1 mole of N2 / 2 mole of NH3) = 1:2

How to convert mole fraction into molarity and morality?

Mole fraction to molality:

Molality = mole fraction of solute/ mass of solvent in Kg

Mass of solvent in Kg = mole fraction of solvent x molar mass of solvent / 1000

Mole fraction to Molarity:

  • We need the density of the solution = d
  • The volume of solution in liters = mass of the solute in Kg/density of the solution
  • Molarity = mole fraction of the solute/volume of solution in a liter