How is glucose prepared from starch ?

Explanation

When starch is boiled with dilute `H_(2)SO_(4)` at 393 K under pressure it undergoes hydrolysis to give glucose. Completing the reaction, excess `H_(2)SO_(4)` neutralized by addition chalk powder and solution is decolourized by activated charcoal.
`underset("Starch")((C_(6)H_(10)O_(5))_(n))+nH_(2)O underset(393K,2-3 " atm")overset("dil."H_(2)SO_(4))rarr underset("Glucose")(nC_(6)H_(12)O_(6))`