Which of the following will react with water?

\(Cl_3CCHO\)

The answer is (2) \(Cl_3CCHO\).

Out of the four compounds listed, only chloral \((Cl_3CCHO)\) will react with water. Chloral is a chlorinated aldehyde, and it is the only compound listed that has a carbonyl group. When chloral reacts with water, it forms chloral hydrate, which is a white solid.

The other compounds listed will not react with water. \(CHCl_3\) (chloroform) is a chlorinated hydrocarbon, and it is not reactive with water. \(CCl_4\) (carbon tetrachloride) is a fully chlorinated hydrocarbon, and it is even less reactive with water than chloroform. \(ClCH_2CH_2Cl\) (1,2-dichloroethane) is a chlorinated alkane, and it is also not reactive with water.

Therefore, the only compound that will react with water is chloral.