Q.
Show with diagrams why hydrochloric acid is used in the test for non-reducing sugars (e.g. sucrose)

A.
Sucrose is a combination of two simple sugars, fructose and glucose. The two simple sugars are combined in a way that gives a negative test for glucose or other reducing sugars. Hydrochloric acid will cause sucrose to break down into the two simple sugars from which it is composed. Study the diagrams below:

Glucose (or other reducing sugar) -----> Positive Benedict test

Sucrose (or other non-reducing sugar) ----> Negative Benedict test

Sucrose + HCl -------> glucose + fructose ----> Positive Benedict test

You can improve on the above diagrams if you spend enough time to understand them.