In the previous posts, we have studied in detail, how to find n-factor and equivalent weight for a number compounds. In this post we shall talk more about the actual concentration term- normality.

As studied in post #143, normality term gives us the # of gram equivalents per litre of the solution. This means that if we dissolve 1g equivalent weight of a substance to make 1 litre of solution, we would get 1N solution of that substance.

So,

If we dissolve **49g** of H_{2}SO_{4} in 1 litre of water , we will get **1N H _{2}SO_{4} solution**.

If we dissolve

**62g**of boric acid in 1 litre of water , we will get

**1N boric acid solution**.

If we dissolve

**40g**of NaOH in 1 litre of water , we will get

**1N NaOH solution**.

**Relationship between Molarity and Normality**

**N = n _{f }× M**

Normality is not a very frequently used concentration term due to its limitations. The biggest limitation of this term is that it depends on the chemical reaction under consideration. *Thus, a solution of H _{2}SO_{4} has a fixed molarity but normality depends on how it reacts in a reaction!*

We use this term in titrimetric calculations.(*We will learn those calculations when we study titrations in detail*).

**5.Weight,Volume and Weight to volume ratios **

There are many units under this section which express the concentration in weight to volume ratio-

No. | Concentration unit | Denoted as | Definition | Type |

1. | weight percent | %w/w | grams of solute per 100g of solution | Weight to weight ratio |

2. | Volume percent | %v/v | mL of solute per 100mL of solution | Volume to volume ratio |

3. | weight to volume percent | %w/v | grams of solute per 100mL of solution | weight to volume ratio |

4. | parts per million | ppm | i)micrograms of solute per gram of solutionorii)milligrams of solute per liter of dolution( aq solutions) | weight to volume ratio |

5. | parts per billion | ppb | Nanograms of solute per gram of solution or micrograms of solute per liter of solution. | weight to volume ratio |

**6. p-function**.

Sometimes during a reaction , a reactant’s concentration may change by many orders of magnitude. In such a case, plotting a graph of the change of concentration as function of time or volume of reagent is a more convenient way to study the reaction. In such cases, we express concentration as a p-function.

**p-function of a number X is the negative log of that number.**

**pX = –log(X)**

*e.g*.-pH = –log[H+] = –log(0.10) = 1.00…the pH of a solution that is 0.10 M H+ is 1.

We can easily plot [H+] (* on y-axis*) vs volume of Base added to it(

*) and study the reaction graphically! We will see these kind of reactions in the titration chapter, which we shall study soon.*

**on x-axis**In the next post we shall start solving problems relating to various concentration terms.Till then,

Be a perpetual student of life and keep learning…

Good day !