How to Calculate the Molar Concentration

Molar concentration indicates how much of a chemical is dissolved in a solution.

Molar concentration refers to the measurement of a substance that is dissolved in a liquid over a given volume. Molar concentration may also be referred to as the molarity of a substance. For example the molarity of seawater is the concentration of salt in a specific measurement of seawater. Molar concentration can be calculated using the following equation: c=n/v. C equals the molarity of the substance, n is the amount of solute in moles and v is the volume being measured.

Things You'll Need

• Atomic structure of substance
• Periodic table with atomic mass
• Mass of substance
• Volume of liquid
• Calculator
• Pencil
• Paper

Instructions

1. Determine the atomic structure of the substance dissolved. An example is acetic acid. This has an atomic structure with a carbon atom, two oxygen atoms and four hydrogen atoms. The atomic mass of carbon is 12, oxygen is 16 and hydrogen is 1, so the total molar mass of acetic acid is 48.

2. Convert the volume of the liquid into liters. Write down this measurement.

3. Multiply the volume of the liquid by the molar mass of the solute. Divide the mass of the solute by this number. For example, to determine the molarity of acetic acid dissolved in 155 milliliters of liquid, the following formula should be used (the asterisk indicates multiplication):

   1.24 g / (48 * .155) = .167M

   1.24 is the mass of the acetic acid in grams, 48 is the molar mass and .155 is the volume; the molar concentration is .167.

Tips & Warnings

• Molar concentration always uses metric measurements of liters.

References

• Tutor Vista: Molar Concentration Formula
• Emporia: Molar Concentration
• Calculator: Units Converter for Molar Concentration