(a) What type of deviation from Raoult's law is shown by a mixture of ethanol and acetone? Give reason. OR (b) Define Azeotrope. What type of azeotrope is formed by negative deviation from Raoult's law? Give an example.

Option (a) Solution

Step 1 (Identification of Deviation): [1 Mark]

A mixture of ethanol ($C_2H_5OH$) and acetone ($CH_3COCH_3$) shows positive deviation from Raoult's law.

Step 2 (Reasoning based on Molecular Interactions): [1 Mark]

• In pure ethanol, molecules are strongly held together by intermolecular hydrogen bonding.
• On adding acetone, its molecules get in between the ethanol molecules and break some of the hydrogen bonds.
• This weakens the intermolecular attractive forces,