Which of the following substances when boiled with aqueous solution of sodium hydroxide would be hydrolyzed? i. Protein ii. Fat iii. Polythene

Analyze the question: We need to find which substances break down (hydrolyze) when boiled with aqueous NaOH.

Concept:

• Proteins are polymers of amino acids joined by peptide (amide) bonds. Boiling with aqueous alkali (or acid) breaks these bonds, giving salts of amino acids.
• Fats are esters of glycerol and fatty acids. Boiling with aqueous NaOH hydrolyzes the ester linkages. This is saponification, giving glycerol and sodium salts of fatty acids (soap).
• Polythene is an addition polymer of ethene with only C-C and C-H bonds. It is chemically inert and has no ester or amide link to attack, so alkali does not hydrolyze it.

Step-by-step solution:

1. Protein: contains -CONH- (peptide) links, which are hydrolyzed by NaOH. ✔
2. Fat: contains -COO- (ester) links, which are hydrolyzed (saponification): Fat + 3NaOH → Glycerol + 3 Soap (RCOONa) ✔
3. Polythene: (-CH₂-CH₂-)ₙ is saturated and unreactive towards alkali. ✘

So only i (protein) and ii (fat) are hydrolyzed.

Correct answer: C. i and ii

Exam tip: Remember that hydrolysis targets the "functional links": esters (fats, oils) and amides (proteins, nylon) break down. Addition polymers like polythene, PVC and polystyrene have only C-C backbones and resist hydrolysis. Quick memory: "Fats and proteins break, polythene stays."