A **solution** is defined as a homogeneous mixture of two or more chemically non reacting substances, the relative amount of which can be varied up to a certain limit.

If a solution consist of only two components it is called a **binary solution.**

The component present in smaller amount is called **solute** while the other present in larger amount is called **solvent**

The concentration of the solution can be expressed in number of ways:

**(1) Mass percent or weight percent** :Mass percent of a solute in a solution is the mass of the solute in grams present in 100 grams of solution.

**(2) Strength**: Strength of a solution is defined as the amount of the solute in grams present per litre of the solution.

**(3) Molarity:** Molarity of a solution is defined as the number of moles of the solute present per litre of the solution.It is represented by the symbol, M.

**(4) Molality** :The molality of a solution is defined as number of moles of the solute dissolved in 1 kg of the solvent.

It is represented by the symbol m.

**(5) Normality** : Normality of a solution is defined as the number of gram equivalent of the solute present per litre of the solution.

It is represented by the symbol N.

**Basicity** is the number of displaceable H^{+} ions present in 1 molecule of the acid.

**Acidity** is the number of displaceable OH^{–} ions present in 1 molecule of the base.

**(6) Mole fraction** : Mole fraction of any component in the solution is equal to the number of moles of that component divided by the total number of moles of all the components.

For a solution containing n_{2} moles of the solute dissolved in n_{1} moles of the solvent,

**(7) Parts per million**: The concentration of very dilute solution is expressed in terms of parts of the solute by mass present in million parts by mass of the solution.

**Molarity equation**

If a solution having molarity M_{1} and volume V_{1} is diluted to volume V_{2} so that the new molarity is M_{2} then as the total number of moles in the solution remains the same, we have :

**Normality Equation**

**Relation between molarity and normality of the solution of an acid or base**

Normality of solution of an acid = Molarity × Basicity

Normality of solution of a base = Molarity × Acidity

**Calculation of Molarity and Normality of the solution obtained on mixing two or more solution**

If the solutions mixed are of the same substance

If V_{1} mL of a solution of molarity M_{1} are mixed with V_{2} mL solution of the same substance with molarity M_{2} Or V_{1} mL of M_{1} HCL solution are mixed with V_{2} mL of M_{2} , then the molarity of the solution obtained is calculates as:

M_{1} V_{1} + M_{2} V_{2} = M_{3} (V_{1} +V_{2})

N_{1}V_{1} + N_{2}V_{2} = N_{3} (V_{1} +V_{2})

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