Question

What would you observe in the following case:

Sugar crystals are added to a hard glass test tube containing concentrated Sulphuric acid.

Answer 1

Dehydration of Sugar crystal:

• When sugar crystals are added to the conc. Sulphuric acid, a black residue of carbon is formed.
• In this reaction, conc. Sulphuric Acid is a Dehydration agent because water molecules are eliminated from sugar.

Balanced chemical equation:

$\underset{\mathrm{Sugar}\mathrm{crystals}}{{\mathrm{C}}_{12}{\mathrm{H}}_{22}{\mathrm{O}}_{11}\left(\mathrm{s}\right)}\stackrel{\mathrm{conc}.{\mathrm{H}}_2{\mathrm{SO}}_4}{\to }\underset{\mathrm{Carbon}(\mathrm{Black}\mathrm{coloured})}{12\mathrm{C}\left(\mathrm{s}\right)}+\underset{}{({\mathrm{H}}_2{\mathrm{SO}}_4+11{\mathrm{H}}_2\mathrm{O})}$

Therefore, when concentrated Sulphuric acid (${\mathrm{H}}_2{\mathrm{SO}}_4$) is added to a hard glass tube containing sugar crystals, a black residue of Carbon is observed.