Problem 2 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

In the following reactions, products (A) and (B), respectively, are. [Main Jan. 07, 2020 (II)] \(\mathrm{NaOH}+\mathrm{Cl}_{2} \rightarrow(\mathrm{A})+\) side products (hot and conc.) \(\mathrm{Ca}(\mathrm{OH})_{2}+\mathrm{Cl}_{2} \rightarrow(\mathrm{B})+\) side products (dry) (a) \(\mathrm{NaClO}_{3}\), and \(\mathrm{Ca}(\mathrm{OCl})_{2}\) (b) \(\mathrm{NaClO}_{3}\) and \(\mathrm{Ca}\left(\mathrm{ClO}_{3}\right)_{2}\) (c) \(\mathrm{NaOCl}\) and \(\mathrm{Ca}(\mathrm{OCl})_{2}\) (d) \(\mathrm{NaOCl}\) and \(\mathrm{Ca}\left(\mathrm{ClO}_{3}\right)_{2}\)

Step-by-Step Solution

Answer

Products A and B are \( \text{NaClO}_3 \) and \( \text{Ca(OCl)}_2 \), respectively.

Step 1: Analyze Reaction 1

The first chemical reaction is \( \text{NaOH} + \text{Cl}_2 \rightarrow (A) + \text{side products (hot and conc.)} \). When chlorine gas reacts with hot and concentrated sodium hydroxide, the main product formed is sodium chlorate, \( \text{NaClO}_3 \). We can derive the reaction as follows: \( 3\text{Cl}_2 + 6\text{NaOH} \rightarrow 5\text{NaCl} + \text{NaClO}_3 + 3\text{H}_2\text{O} \). Thus, \( A \) is \( \text{NaClO}_3 \).

Step 2: Analyze Reaction 2

The second reaction is \( \text{Ca(OH)}_2 + \text{Cl}_2 \rightarrow (B) + \text{side products (dry)} \). When calcium hydroxide reacts with dry chlorine, bleaching powder, \( \text{Ca(OCl)}_2 \), is formed. The relevant reaction is: \( \text{Ca(OH)}_2 + \text{Cl}_2 \rightarrow \text{Ca(OCl)}_2 + \text{H}_2\text{O} \). Therefore, \( B \) is \( \text{Ca(OCl)}_2 \).

Step 3: Combine Results

Now combine the results from Steps 1 and 2: \( A = \text{NaClO}_3 \) and \( B = \text{Ca(OCl)}_2 \). This matches option (a): \( \text{NaClO}_3 \) and \( \text{Ca(OCl)}_2 \). Thus, the products formed are consistent with option (a).

Key Concepts

Chemical Reactions

Chemical reactions are processes where substances transform into new products by breaking and forming chemical bonds. In the context of inorganic chemistry, these reactions often involve simple compounds. When substances like sodium hydroxide (\( \text{NaOH} \)) and chlorine gas (\( \text{Cl}_2 \)) react, new compounds are formed. For example, when chlorine reacts with hot and concentrated sodium hydroxide, sodium chlorate (\( \text{NaClO}_3 \)), a product of this chemical reaction, is produced.
Understanding chemical reactions involves predicting how different substances interact based on their chemical properties. Chlorine, being highly reactive, can form a variety of compounds depending on the conditions. Some reactions may release energy or absorb it, resulting in exothermic or endothermic processes respectively.
This transformation process has real-world applications, such as the production of materials used in disinfection and cleaning, highlighting the importance of understanding basic chemical reaction processes.

Sodium Chlorate

Sodium chlorate (\( \text{NaClO}_3 \)) is an inorganic compound that is often used as a herbicide. It is colorless and soluble in water, showcasing its properties as an effective oxidizing agent. It is typically produced through the reaction of chlorine with sodium hydroxide under specific conditions such as high temperature.
To synthesize sodium chlorate, the balanced equation is: \[ 3\text{Cl}_2 + 6\text{NaOH} \rightarrow 5\text{NaCl} + \text{NaClO}_3 + 3\text{H}_2\text{O} \] This equation demonstrates how multiple molecules interact to yield sodium chlorate as a key product. Due to its oxidizing capabilities, sodium chlorate is widely used in the paper industry for bleaching and also as a precursor for other chemicals.
Safety is vital when handling sodium chlorate since it can promote combustion. Its storage and handling require consideration to prevent unintentional fires or explosions.

Bleaching Powder

Bleaching powder is a compound known chemically as calcium hypochlorite (\( \text{Ca(OCl)}_2 \)). Derived from the reaction of calcium hydroxide with chlorine gas, it serves as an essential disinfectant and a bleaching agent. This compound finds applications in water treatment and sanitation.
The reaction to produce bleaching powder can be expressed as:\( \text{Ca(OH)}_2 + \text{Cl}_2 \rightarrow \text{Ca(OCl)}_2 + \text{H}_2\text{O} \). This reaction reflects how calcium ions combine with chlorine to form the active bleaching agents used in many cleaning products. The accessible chlorine in the compound makes it effective for killing germs and bacteria.
Bleaching powder, being an important chemical in everyday cleaning and public health, emphasizes the practical significance of chemical products in inorganic chemistry. It's crucial to store bleaching powder correctly to prevent loss of chlorine and to maintain its effectiveness.