Problem 143 - A Complete Resource Book in Chemistry for JEE Main

Question

Sulphur reacts with chlorine in the ratio \(1: 2\) and forms X. X on hydrolysis gives a sulphur compound Y. What is the hybridized state of central atom in the anion of \(Y\) ? (a) \(\mathrm{sp}^{3} \mathrm{~d}\) (b) \(s p^{2}\) (c) \(\mathrm{sp}^{3}\) (d) sp

Step-by-Step Solution

Answer

The hybridized state of the central atom in \((\text{S}_2\text{O}_3)^{2-}\) is \(\text{sp}^3\).

Step 1: Identify the Reaction Products

When sulphur reacts with chlorine in the ratio of 1:2, it forms sulphur dichloride, which is denoted as \(\text{SCl}_2\).

Step 2: Hydrolysis of SCl2

Sulphur dichloride \(\text{SCl}_2\) undergoes hydrolysis to form thiosulfuric acid \((\text{H}_2\text{S}_2\text{O}_3)\). This can be represented by the reaction: \(\text{SCl}_2 + 2\text{H}_2\text{O} \rightarrow \text{H}_2\text{S}_2\text{O}_3 + 2\text{HCl}\).

Step 3: Identify the Anion in Y

Upon hydrolysis, the sulphur compound \(Y\) is \(\text{H}_2\text{S}_2\text{O}_3\). The anion formed is the thiosulfate ion \((\text{S}_2\text{O}_3)^{2-}\).

Step 4: Determine Hybridization in Thiosulfate Ion

In the thiosulfate ion \((\text{S}_2\text{O}_3)^{2-}\), one of the central sulfur atoms is surrounded by one other sulfur atom, an oxygen atom, and a negative charge associated with the ion. This indicates that it is \(\text{sp}^3\) hybridized, since it forms four sigma bonds or lone pairs.

Key Concepts

Sulphur Dichloride

Sulphur dichloride, chemically represented as \( \text{SCl}_2 \), is a compound formed when sulfur reacts with chlorine in a 1:2 molar ratio. This means for every one sulfur atom, two chlorine atoms are involved in the reaction. Sulphur dichloride is an essential compound in various chemical processes and is known for its reactive nature.

• It appears as a reddish-brown liquid under standard conditions.
• It typically exhibits a pungent smell, similar to that of chlorine gas.
• This compound is often used as an intermediate in the synthesis of other chemicals.

Sulphur dichloride is quite reactive due to the polar nature of the S-Cl bonds, as chlorine atoms are more electronegative than sulfur. This polarity makes \( \text{SCl}_2 \) highly susceptible to reacting with water, leading us to the next concept: hydrolysis.

Hydrolysis

Hydrolysis is a type of chemical reaction where a compound reacts with water, leading to the breakdown of that compound. With sulphur dichloride \( (\text{SCl}_2) \), hydrolysis occurs quite readily, as water interacts with the chlorine atoms to form thiosulfuric acid \((\text{H}_2\text{S}_2\text{O}_3)\).
The balanced chemical equation for this reaction is:\[\text{SCl}_2 + 2\text{H}_2\text{O} \rightarrow \text{H}_2\text{S}_2\text{O}_3 + 2\text{HCl}\]During hydrolysis, chloride ions (\( \text{Cl}^- \)) are replaced by hydroxide ions (\( \text{OH}^- \)) from water, effectively breaking the chlorine-sulfur bonds. This reaction results in the formation of thiosulfuric acid, and concurrently, hydrochloric acid (\( \text{HCl} \)) is released as a byproduct. Understanding hydrolysis is crucial as it explains how compounds decompose in aqueous environments, often setting the stage for further reactions.

Thiosulfate Ion

The thiosulfate ion, denoted as \((\text{S}_2\text{O}_3)^{2-}\), is a polyatomic ion that emerges from the hydrolysis of \( \text{H}_2\text{S}_2\text{O}_3 \) or the thiosulfuric acid. This ion is noted for its stability in various chemical reactions and predominantly appears in solutions such as fixatives for photography and certain medicinal applications.

• In the \((\text{S}_2\text{O}_3)^{2-}\) ion, sulfur atoms can be understood in terms of oxidation states; one sulfur in the reduced form and another in the higher oxidation state linked to the oxygen atoms.
• The geometry and hybridization play a significant role in the ion's behavior and stability.

Concerning hybridization, one sulfur atom in the thiosulfate ion is \( \text{sp}^3 \) hybridized. This sulfur is bonded with another sulfur, bonded with an oxygen, and has a lone pair giving it a tetrahedral shape typical of \( \text{sp}^3 \) hybridized atoms. Understanding the hybridization and structure of the thiosulfate ion can help explain its reactions and interactions with other compounds.