Concentration of solution corresponds to the amount of solute present in the given amount of solution. There are different units to explain the concentration of solution.

**Units of concentration:**

**1. Percentage of solution:**

It is the no. of part of solute present in 100 parts of solution. Percentage of solution can be expressed either in W/W, W/V or V/V

**2. Normality of Solution (eqv.l-1 or N)**

It is defined as the no. of gram eqv. of solute present in 1L of its solution.

Mathematically,

A solution is said to have concentration 1 normal (1N), decinormal (N/10) and centinormal (N/100) as 1,0.1,0.01 gm eqv. Of solute are present in 1L of solution respectively.

**3. Molarity of solution (moml L-1 or M)**

It is defined as the no. of g. mol. Of solute present in 1L of its solution.

Mathematically,

A solution is said to have concentration 1 molar (1M), decimolar (M/10) and centimolar (M/100) as 1, 0.1 and 0.01 g. mol. Of solute are present in 1L of its solution respectively.

**4. Gram/L (gL-1)**

It is defined as the no. of gm of solute present in 1L of solution. gL-1 can be related to normality (N) and molarity (M) ad thereby normality and molarity can be related to one another and it is reduced as follows:

gL-1 = Normality x eqv. wt. → 1

Similarly,

gL-1 = molarity x mol. Wt. → 2

then from equation 1 and 2. We get,

Normality x eqv. wt. = molarity x mol. Wt.

This expression says, normality and molarity of solution becomes identical only if eq. wt. and mol. wt. are same.

**5. Molarity (mol Kg-1 or m)**

Molarity is defined as the no. of moles of solute present in 1 kg. of solvent.

Mathematically,

A solution is said to have 1 molar concentration when 1 mole of solute is present in 1 kg of solvent.

**6. Mole Fraction (x)**

Mole fraction is the fraction of total no. of mole of a compound present in the mixture.

Let us consider a solution containing n1 mole of solvent and n2 mole of solute.

Here, x1 + x2 = 1

**7. Part per million (PPM)**

Part per million is the no. of part of solute present in 1 million part of solution.

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