📘 Raoult’s Law – Introduction

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📘 Raoult’s Law – Introduction

(Class 12 Chemistry – NCERT Chapter 1: Solutions)

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👨‍🔬 Who Gave It?

Francois Marte Raoult, a French chemist, proposed this law in 1886.
He gave a quantitative relationship between vapour pressure and composition of a solution containing volatile liquids.

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💡 Raoult’s Law – Statement:

In a solution of volatile liquids, the partial vapour pressure of each component is directly proportional to its mole fraction in the liquid phase.

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🧪 Mathematical Form:

For a component 1:

$$p_1 = x_1 \cdot p_1^0$$

Where:

• $p_1$ = partial vapour pressure of component 1 in the solution

• $x_1$ = mole fraction of component 1 in the liquid

• $p_1^0$ = vapour pressure of pure component 1 at the same temperature

🔁 Similarly, for component 2:

$$p_2 = x_2 \cdot p_2^0$$

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🧠 Key Idea:

The more the mole fraction of a component in the liquid phase, the greater its contribution to the total vapour pressure.

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Would you like the complete derivation with total vapour pressure, Dalton’s law, and the graph (Fig 2.3) next?