Explanation:

Hydrates are the compounds which contain water molecules in their structure. Aldehydes can form hydrates by adding water across the carbonyl group. The hydrate formation depends on the presence of alpha-hydrogen atom in the aldehyde molecule.

Trichloroacetaldehyde forms stable hydrate due to the following reasons:

Presence of alpha-hydrogen atom: Trichloroacetaldehyde contains an alpha-hydrogen atom which undergoes hydrate formation.

Electron-withdrawing nature of -Cl groups: The presence of three chlorine (-Cl) groups in trichloroacetaldehyde increases the electron-withdrawing nature of the molecule and makes the carbonyl group more electrophilic. This facilitates the addition of water across the carbonyl group.

Stabilization by intramolecular hydrogen bonding: Upon addition of water, a hydrate is formed which is stabilized by intramolecular hydrogen bonding between the hydroxyl group and the alpha-hydrogen atom. This results in the formation of a cyclic hemiacetal which is stable.

Other aldehydes like formaldehyde, acetaldehyde, and propionaldehyde can also form hydrates but they are less stable compared to trichloroacetaldehyde hydrate.

Conclusion:

Trichloroacetaldehyde forms a stable hydrate due to the presence of alpha-hydrogen atom, electron-withdrawing nature of -Cl groups, and stabilization by intramolecular hydrogen bonding.

In aqueous solution of aldehydes or ketones hydrates are formed if alph - carbonation is more stable or hydrate is stabilized by hydrogen bonding