The key difference between concentration and molarity is that the concentration is the content of solutes in a solution whereas the molarity is the method of expressing the concentration of a solution.
Concentration and molarity are two important phenomena in chemistry. We use both these terms to indicate a quantitative measurement of a substance. If you want to determine the amount of copper ions in a solution, we can give it as a concentration measurement. Similarly, to determine the concentration, we need to have a mixture of components. Moreover, to calculate the concentration of each component’s concentration, we need to know the relative amounts dissolved in the solution. Concentration is the term that we widely use; however, molarity is also a type of concentration measurement.
What is Concentration?
There are a number of methods to measure the concentration. They are mass concentration, number concentration, molar concentration, and volume concentration. We give all these as ratios, where the numerator is representing the amount of the solute, and the denominator is representing the amount of solvent. The way of expressing the solute differs in all these methods.
However, the denominator is always the volume of the solvent. In mass concentration, we give the mass of the dissolved solute in one litre of the solvent. Likewise, in number concentration, we give the number of solutes, and in molar concentration, moles of solute. Further, in volume concentration, we use the volume of the solute.
Other than these, we can give concentrations as mole fractions where we give the moles of the solute in relation to the total amount of substances in the mixture. In the same way, we can use the mole ratio, mass fraction, and mass ratio to indicate concentration. Also, we can show this as percentage values. According to need, we need to select the method of indicating the concentration.
What is Molarity?
Molarity is the molar concentration. This is the ratio of the number of moles of a substance in one volume of a solvent. Conventionally, the solvent volume is given in cubic meters. However, for our convenience, we often use litres or cubic decimeters. Therefore, the unit of the molarity is mol per litre/ cubic decimeter (molL-1, moldm-3). Moreover, we can indicate the unit as M.
Video 01: Molarity Explained
For example, a solution of 1 mol of sodium chloride dissolved in water has a molarity of 1 M. Molarity is the most commonly used method of concentration. For example, we use it in the calculation of pH, the dissociation constants/equilibrium constants etc. Moreover, we need to do the conversion of a mass of a given solute to its molar number in order to give the molar concentration. To do this, we need to divide the mass by the molecular weight of the solute. For example, if want to prepare a 1 M of potassium sulfate solution, 174.26 g mol-1 (1 mol) of potassium sulfate should be dissolved in one litre of water.
What is the Difference Between Concentration and Molarity?
Molarity is a method of expressing the concentration of a solution. Therefore, the key difference between concentration and molarity is that the concentration is the content of solutes in a solution whereas the molarity is the method of expressing the concentration of a solution. Moreover, we can determine the concentration as mass concentration, number concentration, molar concentration, and volume concentration. But we can determine the molarity as molar concentration only. Further, the unit of measurement of concentration is according to the method we use to determine the concentration whereas the unit of measurement for molarity is mol/L.
Summary – Concentration vs Molarity
Molarity is a way of expressing the concentration. The key difference between concentration and molarity is that the concentration is the content of solutes in a solution whereas the molarity is the method of expressing the concentration of a solution.
1. Helmenstine, Anne Marie, Ph.D. “Concentration Definition (Chemistry).” ThoughtCo, Jun. 22, 2018. Available here
2. “Molar Concentration.” Wikipedia, Wikimedia Foundation, 2 Dec. 2018. Available here
1.”Dilution-concentration simple example”By FirstPrinciples (Public Domain) via Commons Wikimedia