Answer the following question from the passage below:

The process of accumulation of molecular species at the surface of solid or liquid is called adsorption. It may be physisorption or chemisorption. Low temperature is favorable for physisorption. Amount of gas adsorbed by a solid depends upon nature of gas. Easily liquifiable gases are readily adsorbed. Catalyst increases the rate of reaction. Catalysis may be homogenous or heterogenous Enzymes are biological catalysts. They work at optimum pH and temperature. Solutions are of three types i.e. true solutions, colloids and suspensions. Depending on the interaction between dispersed phase and dispersion medium colloids may be Lyophilic and Lyophobic. Depending on type of particles there may multimolecular, macro-molecular and associated colloids. Sol. gel, emulsions are also various types of colloids.

An example of homogenous catalysis is:

\(2SO_2 (g) + O_2(g) \overset{NO (g)}{\longrightarrow}2SO_3 (g)\)

The correct answer is option 4. \(2SO_2 (g) + O_2(g) \overset{NO (s)}{\longrightarrow}2SO_3 (g)\).

In chemistry, catalysis is the process where a substance increases the rate of a reaction without being consumed itself. The special substance that speeds things up is called a catalyst. There are two main types of catalysis based on the phases of the catalyst and reactants:

Homogeneous Catalysis: Here, the catalyst is in the same phase as the reactants. This phase is typically a liquid solution, but it can also be a gas phase.

Heterogeneous Catalysis: In contrast, heterogeneous catalysis involves a catalyst in a different phase from the reactants. Commonly, the catalyst is a solid, and the reactants are gases or liquids.

Let us break down your answer choices based on this concept:

\(2SO_2 (g) \overset{Pt (s)}{\longrightarrow} 2SO_3 (g)\): Here, the catalyst \((Pt)\) is a solid, while the reactants (\(SO_2\) and \(SO_3\)) are gases. This is an example of heterogeneous catalysis.

\(N_2 (g) + 3H_2 (g) \overset{Fe (s)}{\longrightarrow}2NH_3 (g)\): Similar to option 1, Fe (catalyst) is a solid, and \(N_2\), \(H_2\), and \(NH_3\) (reactants) are gases. This is again heterogeneous catalysis.

\(4NH_3(g) + 5O_2(g) \overset{Pt (s)}{\longrightarrow} 4NO(g) + 6H_2O(g)\): Pt acts as a catalyst, but it's still in a different phase (solid) than the gaseous reactants (\(NH_3\), \(O_2\), \(NO\), and \(H_2O\)). This is heterogeneous catalysis.

\(2SO_2 (g) + O_2(g) \overset{NO (g)}{\longrightarrow}2SO_3 (g)\): Here, both the catalyst (NO) and the reactants (SO2 and O2) are in the same phase (gas). This is a classic example of homogeneous catalysis.

Key takeaway: In homogeneous catalysis, the catalyst mingles freely with the reactants in the same phase, like a friend joining the party. In heterogeneous catalysis, the catalyst acts more like a separate tool or machine that the reactants interact with at an interface.