Problem 105 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is an example of homogeneous catalysis reaction? (1) \(2 \mathrm{SO}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \stackrel{\mathrm{NO}(\mathrm{g})}{\longrightarrow} 2 \mathrm{SO}_{3}(\mathrm{~g})\) (2) Hydrolysis of aqueous sucrose solution in the presence of aqueous mineral acid (3) \(2 \mathrm{H}_{2} \mathrm{O}_{2}(\mathrm{l}) \stackrel{\mathrm{Pl}(\mathrm{s})}{\longrightarrow} 2 \mathrm{H}_{2}(\mathrm{I})+\mathrm{O}_{2}(\mathrm{~g})\) (4) hydrolysis of liquid ester in the presence of aqueous mineral acid (a) 2 and 4 (b) 2 and 3 (c) 1,2 and 3 (d) 1,2 and 4

Step-by-Step Solution

Answer

Option (d) 1, 2, and 4 are examples of homogeneous catalysis reactions.

Step 1: Identify Homogeneous Catalysis

Homogeneous catalysis occurs when the reactants and the catalyst are all in the same phase, typically all gases, all liquids, or all in solution (aqueous). Let’s analyze the options to find which reactions have the catalyst in the same phase as the reactants.

Step 2: Analyze Option 1

In reaction (1), \ 2 \ \mathrm{SO}_{2} (g) + \mathrm{O}_{2} (g) \stackrel{\mathrm{NO} (g)}{\longrightarrow} 2 \ \mathrm{SO}_{3} (g) \, the catalyst \(\mathrm{NO}\) is in the gaseous phase along with reactants \(\mathrm{SO}_{2}\) and \(\mathrm{O}_{2}\). Thus, this is an example of homogeneous catalysis.

Step 3: Analyze Option 2

In the hydrolysis of aqueous sucrose solution in the presence of aqueous mineral acid, both the reactants and the catalyst are in aqueous phase. Hence, this reaction is a homogeneous catalysis.

Step 4: Analyze Option 3

For reaction (3), \ 2 \ \mathrm{H}_{2} \mathrm{O}_{2} (l) \stackrel{\mathrm{Pl} (s)}{\longrightarrow} 2 \ \mathrm{H}_{2} (l) + \mathrm{O}_{2} (g) \, the catalyst \(\mathrm{Pl}\) is solid while the hydrogen peroxide is liquid, indicating this is not homogeneous.

Step 5: Analyze Option 4

In the hydrolysis of liquid ester in the presence of aqueous mineral acid, the reactants are in liquid and the catalyst is aqueous, which can be considered homogeneous in certain contexts where aqueous solutions interact with liquids extensively.

Step 6: Determine the Correct Answer

From the analysis: - Option 1 is homogeneous due to all reactants and catalyst being gases. - Option 2 is homogeneous due to all components being in aqueous. - Option 4 can be considered homogeneous due to the liquid phase being compatible with the aqueous catalyst. Thus, the correct answer is (d) 1, 2, and 4.

Key Concepts

Reaction Kinetics

Reaction kinetics is a vital field in chemistry that focuses on the speed or rate at which chemical reactions occur. Understanding how fast a reaction proceeds helps chemists design processes that maximize efficiency. Many factors affect reaction kinetics, including temperature, concentration, and the presence of catalysts. To fully grasp this concept, one must consider how these variables influence the movement and encounter of molecules.
Consider a scenario where a catalyst is used. Catalysts are substances that speed up chemical reactions without being consumed in the process. They're particularly interesting because they provide an alternative pathway with a lower activation energy, hence accelerating the reaction. The quicker a reaction reaches completion, the more efficient it is in a practical context, such as in industrial chemical production or even within biological systems like enzyme action.

• The catalyst remains unchanged after the reaction.
• A lower activation energy means molecules need less energy to react, speeding up the process significantly.

Phase of Matter

Matter exists in different phases, commonly known as solid, liquid, gas, and plasma. These phases depend on temperature and pressure conditions. Understanding these phases helps us grasp how substances interact through chemical reactions. Phases are crucial when analyzing homogeneous and heterogeneous catalysis.
In homogeneous catalysis, both the reactants and the catalyst are in the same phase. A common scenario is when all participants are gases or in a solution. This aspect ensures that the reactants and the catalysts mix uniformly, promoting interaction.

• Gas phase: All molecules are well-distributed, allowing consistent catalysis.
• Aqueous phase: Everything dissolves in water or another solvent, providing close contact during the reaction.

In contrast, heterogeneous catalysis involves different phases, such as a solid catalyst in a liquid or gas. Here, the reaction typically occurs on the surface of the solid catalyst, emphasizing the importance of surface area and physical interactions.

Chemical Reactions

Chemical reactions involve rearranging atoms to form new substances. They play an integral role in both natural processes and industrial applications. At the core of these reactions lies the principle of conservation of mass where reactants transform into products while retaining total mass.
Reaction mechanisms dictate how reactions proceed, highlighting the role of each participating molecule. Homogeneous catalysis showcases a scenario where catalysts effectively alter these mechanisms by lowering energy barriers. This leads to faster product formation without altering the overall essence of chemical change.

• Catalysts are game-changers in chemical reactions, providing speed without being consumed.
• They ensure processes are energy-efficient, reducing resource consumption and enhancing reaction rate.

Ultimately, by adjusting conditions such as the presence of a catalyst, temperature, and concentration, scientists can control and utilize chemical reactions to match their desired outcomes.