what is difference between molarity,molality and normality.please rply

Molarity, molality and normality are three different terms that are used to express the concentration of a solution. 

Molarity is defined as the number of moles of solute present per litre of the solution. Thus 

Molarity =  number of moles of solute / Volume of solution (in litres)

Here number of moles = mass of solute / molar mass of solute

Molality is defined as the number of moles of solute per Kg of the solvent. Thus 

Molality = number of moles of solute / Mass of solvent (in Kg)

Normality of a solution is defined as number of gram equivalents of solute present per litre of the solution. Thus 

Normality = Number of gram equivalents of solute / Volume of solution in litres

The number of gram equivalents are defined as

= mass of solute / equivalent mass

Further the equivalent weight of an element/compound is its atomic/molecular weight divided by its valence (number of electrons gained or lost by one molecule or ion of the substance in the reaction).