Molarity

Introduction

Scientifically, we can say that molarity is the moles of solute per litre of the solution. It is a ratio of the total number of moles of solute in the solution per litre. Molarity is a unit used to measure the concentration of the dissolving substances in a solution. It is named after a German chemist, ‘Molekül,’ is a German word for molecule. It is one of the most common units used to calculate the volume of a solvent or the amount of a solute. When the solvent and the solute blend together to form a solution, the volume of the solution is taken using molarity. The subsequent molarity study material will cover the formula for molarity, units, dilutions, advantages and disadvantages in detail.

What is Molarity?

Molarity can be defined as the total amount of solute (in moles) in the respective solution. It helps find out the concentration of the solute in the given solution. In short, it is a scientific way to describe the number of moles of solute per litre of the liquid. Hence, it can also be called amount concentration or substance concentration. The most commonly used term for molarity is moles per litre in chemistry.

Formula for Molarity :- 

Molarity is the total number of moles of solute for every one litre of the solution. It is derived using the formula given below:

M = Mol solute  ÷  L solution

Here, 

M represents molarity, 

“Mol” represents the number of moles, and

L represents the number of litres.

Units of Molarity :- 

The appropriate unit used to represent the molarity of a molar concentration of a solution is mol/m3. Traditionally, it is used as mol/dm3 or mol/L. Additional units, such as millimolar and micromolar, are represented as mM and μM. If a solution has a molarity concentration of 10 mol/L, it is called a 10 M solution or a concentration value of 10 molars.

Dilutions :-

The process to decrease the solute concentration in the respective solution is known as dilution. This process is undertaken by adding more water (i.e., the solvent) to the solution without making any changes in the solution. The following equation can relate to the concentration of the solutions:

M1V1 = M2V2

Here,

 M1 is referred to as the initial molarity,

V1 is referred to the initial volume,

M2 is referred to as the final molarity, and

V2 is referred to as the final volume.

Advantages of Molarity :- 

The advantages of using molarity as a concentration unit are as follows:

• Convenient to use

Molarity calculations are flexible. The solute can be measured in grams, moles, or based on the volume of the solute. Thus, molarity is very convenient to use.

• Makes further calculations easy

The total molar concentration and the sum of the molar concentration are the same. Hence, these calculations allow further calculations such as calculating the density or the ionic strength.

Disadvantages of Molarity :-

Along with a few advantages, molarity also has disadvantages. Some of them are given below:

• Changes according to the temperature

One of the most significant disadvantages of using molarity to measure the concentration of a solution is it changes according to the temperature. As the temperature increases, molarity decreases. In other words, we can say that it is inversely proportional to the temperature.

• Affected by the pressure

Molarity depends on the volume of the solution. Since the volume of the solution varies as the pressure changes, it affects the molarity of the solution. There is a direct relationship between the pressure and the molarity of the solution. Thus, when the pressure of the solution increases, molarity also increases.

Conclusion

Molarity is one of the most critical units used to derive the concentration of the given solution. The coherent unit to express molarity is mol/L. It is easy to calculate with a simple formula. It can be derived even if the units are in grams, millilitres, or other units. Its flexible nature makes further calculations such as density, volume, or ionic strength easier. However, molarity is volume dependable. Hence, it is affected due to the changing temperature and the changing pressure in the respective solution. It has many different applications in industries, pharmaceutics, and laboratories.