Question

Which colour residue is formed when sugar reacts with sulphuric acid?

• A. Black
• B. No colour change
• C. Red
• D. Slight yellow

Answer 1

The correct option is A

Black

When concentrated sulphuric acid is added to sugar it acts as a dehydrating agent. Dehydrating agents are those substances capable of absorbing the moisture present in the substance. The equation given below is the reaction between sucrose and sulphuric acid.

$C_{12}{H}_{22}{O}_{11}\left(sugar\right)+H_{2}S{O}_4\left(sulphuricacid\right)\to 12C\left(carbon\right)+11H_{2}O\left(water\right)$

This is an exothermic reaction which produces a large amount of heat.

When water is removed from the sucrose compound the remaining product is only carbon atoms and this carbon is the black residue left form the reaction.