Question

What is meant by positive and negative deviations from Raoult's law and how is the sign of ΔsolH related to positive and negative deviations from Raoult's law?

Answer 1

Hey Dear,

◆ Raoult's law -

• Raoult's law states that the mole fraction of the solute component is directly proportional to its partial pressure.

# Positive deviation from Raoult's law -

• Solutions which show higher than expected vapour pressures are said to show positive deviation from Raoult's law.
• For these solutions, ∆solH = positive

# Negative deviation from Raoult's law -

• Solutions which show lower than expected vapour pressures are said to show negative deviation from Raoult's law.
• For these solutions, ∆solH = negative

Thanks dear..

Answer 2

Answer:

positive deviation

(1) A solution or a liquid mixture which has higher vapour pressure than theoretically calculated by Raoult's law or higher than those of pure components is called a nonideal solution with postive deviation.

(2) In these solutions. solute-$olvent intermolecular attractions are weaker than those between solvent- solvent and solute-solute interactions.

(i) For example, solutions of acetone and ethanol, carbon disulphide and acetone, etc.

Negative deviation :

(1) A solution or a liquid mixture which has lower vapour pressure than theoretically calculated by Raoult's law or lower than those of pure components is called a nonideal solution with negative deviation.

(2) In these solutions, the intermolecular interactions between solvent and solute molecules are stronger than solvent-solvent or solute-solute interactions.

(3) For example, solutions of phenol and aniline, chloroform and acetone, etc.