Difference Between Mole and Molarity

Mole vs Molarity
 

Both mole and molarity are related with measuring substances.

Mole

We can count and measure the things we can see and touch. Pencils, books, chairs, houses or anything like that can be easily counted and told in a number, but it is difficult to count the things which are really small. Atoms and molecules in that matter are really small, and there are billions of them in a given tiny space. So attempting to count them as other objects is useless. That is why a measurement unit called “mole” has been introduced. This is used to measure the amount of substances (atoms, molecules, ions, electrons etc.) in chemistry. The symbol of the unit is mol. Carbon 12 isotope is used to define a mole. The number of atoms in 12 grams of pure carbon-12 isotope is known as 1 mol. This value is equivalent to 6.02214179(30) ×10²³ carbon-12 atoms. Therefore, 1mol is 6.02214179(30)×10²³ of any substances. This number is known as the Avogadro’s number. The mass of one mole of a substance expressed in grams is equal to the substance’s molecular weight. If we take a mass of 1 molecular weight, that will contain 1 mol of substances and, therefore, Avogadro’s number of substances. In chemistry, mole is used widely to indicate the measurements instead of volume or weight.

Molarity

Concentration is an important and commonly used phenomenon in chemistry. It is used to indicate quantitative measurement of a substance. If you want to determine the amount of copper ions in a solution, it can be given as a concentration measurement. Almost all the chemical calculations use concentration measurements to draw conclusions about the mixture. To determine the concentration, we need to have a mixture of components. To calculate the concentration of each component’s concentration, the relative amounts dissolved in the solution have to be known. There are few methods to measure the concentration, and molarity is one of them.

Molarity is also known as molar concentration. This is the ratio between numbers 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 liters or cubic decimeters. Therefore, the unit of the molarity is mol per liter/ cubic decimeter (mol l^-1, mol dm^-3). The unit is also indicated as M. For example, a solution of I mol of sodium chloride dissolved in water has a molarity of 1 M.

Molarity is the most commonly used method of concentration measurement. For example, it is used in the calculation of pH, dissociation constants/ equilibrium constants etc. Conversion of a mass of a given solute to its molar number has to be done in order to give the molar concentration. To do this, mass is divided by the molecular weight of the solute. For example, if we 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 liter of water.