Problem 11 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

\(\left[\mathrm{Co}(\mathrm{CN})_{6}\right]^{3-}, \mathrm{Mh} \mathrm{O}_{3}\) The reaction, \(3 \mathrm{ClO}^{-}(\mathrm{aq}) \longrightarrow \mathrm{ClO}_{3}^{-}(\mathrm{aq})+\) \(2 \mathrm{Cl}^{-}(\mathrm{aq})\), is an example of [2001S] (a) oxidation reaction (b) reduction reaction (c) disproportionation reaction (d) decomposition reaction

Step-by-Step Solution

Answer

The reaction is a disproportionation reaction (option c).

Step 1: Define Disproportionation Reaction

A disproportionation reaction is a specific type of redox reaction in which a single substance is simultaneously oxidized and reduced, resulting in two different products.

Step 2: Analyze the Given Reaction

The reaction is \(3\, \text{ClO}^- (aq) \rightarrow \text{ClO}_3^- (aq) + 2\, \text{Cl}^- (aq)\). Here, notice that the \(\text{ClO}^-\) in the reactants is transformed into two different products: \(\text{ClO}_3^-\) and \(\text{Cl}^-\).

Step 3: Identify Oxidation and Reduction Elements

Within the reaction, \(\text{ClO}^-\) is being oxidized to form \(\text{ClO}_3^-\) as chlorine's oxidation state increases, and it is being reduced to form \(\text{Cl}^-\) as chlorine's oxidation state decreases.

Step 4: Conclude the Reaction Type

Since the same substance, \(\text{ClO}^-\), is both oxidized and reduced, this is an example of a disproportionation reaction. This matches the definition provided in Step 1.

Key Concepts

Understanding Oxidation Reactions

Oxidation reactions are processes in which an atom, ion, or molecule loses electrons, resulting in an increase in its oxidation state. Essentially, during oxidation, there is a shift of electrons away from a particular species.
This can often involve the addition of oxygen or the elimination of hydrogen. To easily remember this, you can use the mnemonic: "OIL RIG" - Oxidation Is Loss (of electrons) and Reduction Is Gain (of electrons).

• For an oxidation reaction to occur, another species often accepts the electrons that are being lost. This typically results in a companion reduction reaction, forming what is known as a redox pair.
• Common examples of oxidation include the rusting of iron, where iron is oxidized to form iron oxide.

Understanding the role of oxidation in redox reactions helps in identifying the changing oxidation states and tracing the flow of electrons in chemical processes.

Grasping the Concept of Reduction Reactions

Reduction reactions are just the opposite of oxidation reactions. In these reactions, an atom, ion, or molecule gains electrons, leading to a decrease in its oxidation state. This gain of electrons often involves the removal of oxygen or the addition of hydrogen.
Reduction is crucial because it balances the electron transfer in redox reactions. In every redox reaction, while one species is oxidized, another must be reduced. They go hand in hand.

• An easy way to spot reduction is by looking for a reduction in charge or the addition of electrons in the reaction.
• For example, in the reaction where copper oxide is reduced to metallic copper, electrons are gained by the copper ions to become solid copper.

The importance of reduction reactions extends beyond chemistry; they are vital in biological processes such as respiration and photosynthesis.

Exploring Redox Reactions

Redox reactions, or oxidation-reduction reactions, involve the transfer of electrons between two substances. These types of reactions are characterized by the simultaneous occurrence of oxidation and reduction processes.
This dual process ensures that the electrons lost by one species (oxidation) are gained by another (reduction).

• Redox reactions can be found everywhere, from the batteries that power our gadgets to metabolic processes in living organisms.
• The concept of redox is vital in understanding reaction mechanisms, energy conversions, and electron flow in chemical systems.

By carefully tracking the flow of electrons, chemists can decipher how substances interact and transform, unlocking the details behind many critical processes.