The product obtained, when starch is hydrolyzed with dilute sulphuric acid at 393 K under pressure, is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Glucose only
Starch is a polysaccharide built only of α-D-glucose units joined by glycosidic linkages. Acid hydrolysis breaks every glycosidic linkage and adds a water molecule at each break, so the only product is glucose. This is the commercial method of making glucose: starch is boiled with dilute sulphuric acid at 393 K under a pressure of 2-3 atm.
\( \displaystyle \ce{(C6H10O5)_{n} + nH2O} \xrightarrow[\text{393 K; 2-3 atm}]{\ce{H+}} \ce{nC6H12O6} \)
So the product is glucose only.
Why the other options are incorrect
Option (2) A mixture of glucose and fructose — Incorrect. This is what sucrose gives on hydrolysis, because sucrose is made of one glucose and one fructose unit; starch has no fructose units.
Option (3) Fructose only — Incorrect. Fructose is not a unit of starch, so it cannot be formed from it by hydrolysis.
Option (4) Gluconic acid — Incorrect. It is formed by the oxidation of glucose with a mild oxidising agent such as bromine water, not by hydrolysis.
NCERT (2026-27 edition):
From Starch
