Problem 9 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Chlorine water on standing loses its colour and forms : [Main Online April 11, 2015] (a) HCl only (b) \(\mathrm{HCl}\) and \(\mathrm{HClO}_{2}\) (c) \(\mathrm{HCl}\) and \(\mathrm{HOCl}\) (d) \(\mathrm{HOCl}\) and \(\mathrm{HOCl}_{2}\)

Step-by-Step Solution

Answer

(c) HCl and HOCl .

Step 1: Understanding the Problem

The question is asking what products are formed when chlorine water stands and loses its color. This involves a chemical reaction of chlorine ( Cl_2 ) in water.

Step 2: Write the Chemical Reaction

When chlorine is added to water, it undergoes a hydrolysis reaction to form hydrochloric acid (HCl) and hypochlorous acid (HOCl). The balanced chemical equation is:\[Cl_2 + H_2O \rightarrow HCl + HOCl\]

Step 3: Analyze the Products

The products of the reaction of chlorine with water are hydrochloric acid ( HCl ) and hypochlorous acid ( HOCl ).

Key Concepts

Hydrolysis Reaction

Hydrolysis is a fascinating and important chemical reaction that involves the breaking down of a compound due to a reaction with water. When chlorine (\(Cl_2\)) is dissolved in water, it undergoes hydrolysis. This means water molecules interact with chlorine molecules, leading to a chemical reaction that results in the formation of new compounds.

In the case of chlorine water, the hydrolysis reaction is represented by the equation:\[Cl_2 + H_2O \rightarrow HCl + HOCl\]In this reaction, water (\(H_2O\)) acts as a reactant that transforms chlorine into hydrochloric acid (\(HCl\)) and hypochlorous acid (\(HOCl\)).

• The water molecule provides the necessary environment for the chlorine molecules to form these two acids.
• This chemical process is crucial in both natural environments and industrial applications, affecting everything from water treatment to disinfection.

Understanding hydrolysis reactions like this can help us comprehend how substances change and interact in aqueous solutions.

Chlorine Chemistry

Chlorine is a powerful element often characterized by its strong disinfectant properties. Within chemical reactions, like the one with water, chlorine showcases its versatile reactivity. As a gas in its elemental form (\(Cl_2\)), chlorine is greenish-yellow and can be quite pungent.

When chlorine gas is introduced into water, it undergoes a transformation that illustrates a classic example of chlorine’s chemistry. This process can form various chlorine compounds, such as hydrochloric acid (\(HCl\)) and hypochlorous acid (\(HOCl\)). These compounds are known for their:

• Strong acidic properties.
• Antimicrobial activities, which make them essential in water purification.

Chlorine's behavior and diverse reactions make it an integral component in many everyday applications, ranging from culinary uses to public health initiatives.

Acid Formation

Acids are substances that release hydrogen ions (\(H^+\)) when dissolved in water, and the formation of acids like \(HCl\) and \(HOCl\) in chlorine water is a great example of this process. When chlorine water stands, it leads to the formation of these two prominent acids.

- **Hydrochloric Acid (\(HCl\)):** This is a strong acid commonly found in the stomach, playing a vital role in digestion. It is also widely used in industrial processes.
- **Hypochlorous Acid (\(HOCl\)):** Although weaker than \(HCl\), it is a potent disinfectant, crucial for its ability to kill bacteria and sanitize surfaces.

These acids emerge from the simple interaction of chlorine with water, showing how the basic properties of substances can lead to powerful and useful products through chemical reactions.
Acid formation in chemical reactions showcases the transformative nature of chemistry and how simple compounds can change to become critical substances in both biological and artificial processes.