How To Determine Normality

Normality is a topic of chemistry that is very important and is used for various purposes. It has relation to almost every other unit and makes it hard to remember sometimes, but it is a very important question, either for CBSE or competitive examination.

Normality

Normality is a term of chemistry that is used to measure the concentration of a solution. It is denoted by ‘N’. It is the concentration that’s equivalent to the solution. Normality is used in the calculation of titration.

Normality is basically the number of grams that are equivalent to solute; solute is supposed to be the 1L solution. So, Normality is the number of equivalents of the solute per litre volume of the solution. No. of gram equivalent is the weight of solute multiplied by an equivalent weight of the solute.

How to calculate Normality-

First, find the equivalent weight and calculate that. 

The important thing is to remember that all the units have to be in the exact format that was mentioned. After that, just put the values in the formula.

Molarity-

Molarity is the content present in an appropriate volume. It is the no. of solute per litre of volume in Litre.

Relations between Molarity and Normality-

We know the formula of molarity and normality. Now divide normality by molarity; you will get the number of grams equivalent per number of moles of solute. Since the number of gram equivalent is the mass divided by equivalent mass and the number of moles is mass upon molecular mass.

So from N/M and equivalent mass, we get that N is the product of M and the valence factor.

Differences between Normality and molarity- 

Normality –

• Make use of equivalent weight.
• It is stated as Normality is a number of equivalents of the solute per litre volume of the solution. 
• Unit of normality N

Molarity-

• Make use of molar weight.
• It is stated as the no. of solute per litre of volume in Litre.
• Unit of molarity M

Uses of Normality-

• It determines the presence of H+ and OH- ions in the solution.
• It determines the amount of solution that can be precipitated.
• It determines the acceptance and donation of an electron in a redox reaction.
• Titration is where Normality comes into use the most.

Example- 

1. The first one is going to be 0.15 molar HCl, 1.4 M sulfuric acid, 2 molar sodium hydroxide and 0.4 m barium hydroxide.

Solution- Concentration which is 0.15, is a monoprotic acid. There’s only one hydrogen per formula unit, the son is 1, so it’s going to be point 0.15.

1. What is the normality of a solution that contains 50 gm of H2SO4 dissolved in 15L.

Solution- We’re going to do these two ways. First, we’re going to find the molarity and then find the normality, and then we’re going to use a second method to find normality but without taking molarity into context.

The molarity of a solution is defined as the moles of solute divided by the litres of the solution, so I’m going to start with 50 grams of sulfuric acid. So, sulfuric acid is the solute now.

We’re assuming it’s dissolved in 15 litres of solution, and let’s say that water is the solvent. The first thing you need to do is convert grams to moles. Let’s calculate the molar mass of the ferric acid. The atomic mass of hydrogen is about 1.008; Sulphur is 32.06, and oxygen is 16. The whole mass of sulfuric acid is 98.076. One mole of sulfuric acid has a mass of 98.076 gm. Now the unit grams cancel, so we have moles of solute on top. Now we got divided by the total of the solution, so we have 15 litres of solution. This is going to give us the molarity, moles divided by litres, so it’s 50 divided by 98.075 divided by 15. It’s going to be point 0.03 for M.

It’s the molarity times n, so the molarity is 0.034, and there are two hydrogen atoms per formula unit. This is going to work out to be 0.068, so that’s the normality of the solution, so that’s one way in which you can find it now.

Step by Step Method of Determining Normality

Let’s talk about the other method that we could use, it’s up to you to pick and choose which method works best for you, but I think it’s best to understand it both ways. Now what you need to understand is that normality is defined as the number of equivalence per litre of solution. 

Step one: first, you will convert the gram of substance from one mole of H+. This will give you the number of equivalent weights. That’s how you can find it.

Step two: keep in mind one equivalent weight is the mass that yields 1 mole of H+; that’s why we want to start with one mole of H+. You can convert it directly to normality, where normality is the equivalent weight per litre and then convert directly to normality.

Conclusion- 

Normality is a conclusive and an integrated topic that gives a network of how the units work and their systematics. The units that are integrated with the different other units give you a cohesive structure on how to do questions. If you are interested in the topic of normality, you should look into molarity and molality as well, as they are going to help you in the same way.