When an arsenic-chlorine compound such as AsCl3 interacts with water, which of the following is most likely to occur?

• A. The compound dissolves without any chemical reaction.
• B. Hydrolysis occurs, producing arsenous acid (H3AsO3) and hydrochloric acid (HCl).
• C. No observable change occurs; the compound is inert in water.
• D. A precipitation reaction forms solid arsenic trichloride.

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the nature of the compound AsCl3. It is a covalent arsenic-chlorine compound that can react with water due to the polar nature of the As-Cl bonds and the ability of water to act as a nucleophile.
2. Step 2: Recognize that when certain covalent halides (like AsCl3) interact with water, they often undergo hydrolysis, a chemical reaction where water breaks bonds in the compound, leading to the formation of new products.
3. Step 3: Write the general hydrolysis reaction for AsCl3 with water, where AsCl3 reacts with water molecules to form arsenous acid (H3AsO3) and hydrochloric acid (HCl): \[\mathrm{AsCl_3 + 3H_2O \rightarrow H_3AsO_3 + 3HCl}\]
4. Step 4: Understand that this reaction involves substitution of chlorine atoms by hydroxyl groups from water, producing arsenous acid, a weak acid, and hydrochloric acid, a strong acid, which explains the chemical change observed.
5. Step 5: Conclude that the most likely event when AsCl3 interacts with water is hydrolysis, not simple dissolution without reaction, inertness, or precipitation, based on the chemical behavior of arsenic halides.