CBSE Class 12 Chemistry - Important Formulas all chapters. Learning the important concepts is very important for every student to get better marks in examinations. The concepts should be clear which will help in faster learning. The attached concepts made as per NCERT and CBSE pattern will help the student to understand the chapter and score better marks in the examinations.

**Solution**

**1. Mole fraction (x)**

if the number of moles of A and B are nA and nB respectrively, the mole fraction of A and B will be

X_{A}= X/n_{A}+n_{B} , AND X_{B} = n_{B} / n_{A}+n_{B}

2. **Molarity (M) **= Moles of solute/ Volume of solution in litres

3. **Moality (m) **= Moles of solute / Mass of solvent in kilograms

4. **Parts per million (ppm) **= Number of parts of the component 106 /Total number of parts of all components of the solution

5. **Raoult’s law for a solution of volatile solute in volatile solvent ****:**

p_{A} = p_{A}° x_{A}

p_{B} = p_{B}° x_{B}

Where p_{A} and p_{B} are partial vapour pressures of component ‘A’ and component ‘B’ in solution. p_{A}° and p_{B}° are vapour pressures of pure components ‘A’ and ‘B’ respectively.

6. **Raoults law for a solution of non-volatile solute and volatile ****solvent :**

p °_{A} – p °_{A}/ p °_{A} = *i n _{B} /n_{A} = *

*i W*(for dilute solution)

_{B}* M_{A}/ M_{B}* W_{A}Where xB is mole fraction of solute, *i *is van’t Hoff factor and A A

p °_{A} – p °_{A} / p_{A} ° IS Nrelative lowering of vapour pressure.

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