Home >> Science & Nature >> Science

What Is a Mole Ratio?

Chemists use moles to keep track of the relative amounts of chemicals which combine as reactants are formed as products in a reaction. By doing so, they can readily calculate the optimal ratio in which chemicals should be mixed, to ensure that there is no waste. Molar ratios are one way of using information about a chemical reaction to ensure you are mixing chemicals in the correct proportions.

The Mole
- The mole is the official metric system unit of chemical quantity. It stands for a specific, very large number of atoms or molecules: 6.02 x 10^23 and is sometimes also known as Avogadro's number. The mole is helpful since the quantities of atoms or molecules involved in chemical reactions is typically huge and would be difficult to keep track of. For example, only 12 grams of carbon contains one mole of atoms. Since moles are proportional to atoms or molecules, chemists often use them to keep track of chemical quantities.
Reaction Equations
- The equation of a chemical reaction is a written summary of that particular reaction. It contains a significant amount of information. It shows which chemicals are reacting and which products are formed as a result. For example, the combustion reaction of methane with oxygen to form carbon dioxide and water is written as CH4 + O2 --> CO2 + H2O. A balanced equation also shows the exact proportions in which the chemicals react or are formed.
Balanced Reactions
- In a chemical reaction, atoms are rearranged but not created or destroyed. This means the atoms going into the reaction, on the left hand side of the equation, must equal the atoms going out on the right hand side as products. An equation which has numerical coefficients added so the quantities of atoms of each element are equal on either side is known as a balanced equation. The example equation can be balanced by rewriting it as CH4 + 2O2 --> CO2 + 2H2O.
Mole Ratios
- Once you have a balanced equation, the mole ratios are simply the ratios between the various numerical coefficients of the reactants or products. For example, the mole ratio between methane and oxygen is 1:2. This tells you that you require twice as many moles of oxygen as moles of methane to completely react both those chemicals. Mole ratios can also help you predict the amount of product. The mole ratio between methane and carbon dioxide is 1:1, so you can predict that burning one mole of methane will produce one mole of CO2.

Science