How to Make Molar Solutions

By W D Adkins; Updated April 24, 2017
The solution to a chemical experiment can depend on the solution's molarity.

A solution (or dilution) is composed of a solid substance dissolved in a liquid medium called the solvent. Chemical solutions are widely used in medicine, industry and even for activities in the home. Depending on the purpose, a solution can be measured in terms of the relative weight or volume of the solid to the solvent. A molar solution contains a specified number of moles by weight per unit of solvent. The steps below describe how to make molar solutions.

Understand what a mole is and what a molar solution is. A mole is defined as 6.02 x 10^23 molecules of a substance. This odd number was chosen because the amount in grams of 1 mole of a chemical corresponds closely to its atomic weight. For example 1 mole of water weighs about 18 grams and the atomic weight of a water molecule is about 18. A molar solution contains a specified number of moles of a solid per liter of solvent. For convenience, the steps below assume you are making 1 liter of a molar solution.

Know the chemical reactions that may take place when you add the solvent to the solid. Never neglect this step. Combining some chemicals can be extremely dangerous and even fatal if you are exposed to toxic chemicals produced by a reaction. Always use pure chemicals. For example, use distilled rather than tap water. Tap water contains impurities that can alter the chemical behavior of your solution.

Calculate the amount of solid you need to make molar solutions. To do this, multiply the molar weight of the solid by the concentration (number of moles per liter) of the molar solution you want to make. Then use a scale calibrated in grams to measure out this amount of the solid you need.

Place the solid in an empty 1-liter jar. Add the solvent until you have exactly 1 liter. You may need to stir the solution in order to get the solid to dissolve.

Tip

All solutions have a saturation point. If you try to make a solution that contains more solid than the solvent can dissolve, part of the solid simply won’t dissolve. Be sure the strength of the solution you plan to make is below the saturation point. Be as careful and precise in your measurements as possible. Depending on the purpose of your molar solution, even small errors can ruin a solution.

About the Author

Based in Atlanta, Georgia, W D Adkins has been writing professionally since 2008. He writes about business, personal finance and careers. Adkins holds master's degrees in history and sociology from Georgia State University. He became a member of the Society of Professional Journalists in 2009.