Problem 77 - Chemistry

Question

Describe two reactions in which sulfuric acid acts as an oxidizing agent.

Step-by-Step Solution

Answer

1) Oxidation of Carbon: C + 2H_2SO_4 \rightarrow CO_2 + 2SO_2 + 2H_2O 2) Oxidation of Hydrogen Sulfide: H_2S + 2H_2SO_4 \rightarrow 3S + 2H_2O

Step 1: Reaction 1: Oxidation of Carbon

Sulfuric acid can oxidize carbon in a vigorous reaction. The balanced chemical equation for this reaction is: \[ C + 2H_2SO_4 \rightarrow CO_2 + 2SO_2 + 2H_2O \] In this reaction, sulfuric acid (H_2SO_4) oxidizes carbon (C) to carbon dioxide (CO_2) and is itself reduced to sulfur dioxide (SO_2).

Step 2: Reaction 2: Oxidation of Hydrogen Sulfide

Sulfuric acid also acts as an oxidizing agent when it reacts with hydrogen sulfide. The balanced chemical equation for this reaction is: \[ H_2S + 2H_2SO_4 \rightarrow 3S + 2H_2O \] In this reaction, sulfuric acid (H_2SO_4) oxidizes hydrogen sulfide (H_2S) to sulfur (S) and is itself reduced to sulfur dioxide (SO_2).

Key Concepts

Oxidizing Agent

An oxidizing agent is a substance that gains electrons and causes another substance to lose electrons, thereby undergoing oxidation. In chemical reactions, oxidizing agents play a crucial role in driving the oxidation process. Sulfuric acid (\( H_2SO_4 \)) is a well-known oxidizing agent and participates in various reactions where it accepts electrons from other substances. This electron gain results in the reduction of the oxidizing agent itself. The strength of an oxidizing agent depends on its ability to attract and gain electrons from other substances. In simpler terms, think of the oxidizing agent as the electron "taker," which helps other substances "give away" their electrons or be oxidized.

• Facilitates oxidation by accepting electrons.
• Undergoes reduction as it gains electrons.
• Crucial for redox reactions to occur.

The sulfuric acid in the given reactions is reduced while it oxidizes carbon and hydrogen sulfide.

Carbon Oxidation

In the context of sulfuric acid acting as an oxidizing agent, carbon oxidation is a fascinating chemical process. Carbon is oxidized when it reacts with concentrated sulfuric acid. During this reaction, sulfuric acid accepts electrons from carbon, thus oxidizing it. The overall balanced chemical equation for this reaction is \[ C + 2H_2SO_4 \rightarrow CO_2 + 2SO_2 + 2H_2O \]. Here’s what happens at a deeper level:

• Carbon starts as a zero-oxidation state and ends up as carbon dioxide (\( CO_2 \)), where it is in a +4 oxidation state, showing it lost electrons in the process.
• Sulfuric acid (\( H_2SO_4 \)) oxidizes carbon and is itself reduced to sulfur dioxide (\( SO_2 \)), a +4 state from its original +6 state in sulfuric acid.

Thus, sulfuric acid facilitates the removal of electrons from carbon, transforming it into a more oxidized form. This reaction is an excellent example of how strong oxidizing agents like sulfuric acid participate in redox reactions.

Hydrogen Sulfide Oxidation

Hydrogen sulfide oxidation by sulfuric acid is another important reaction where sulfuric acid acts as an oxidizing agent. In this reaction, sulfuric acid oxidizes hydrogen sulfide (\( H_2S \)), converting it into elemental sulfur (\( S \)). The balanced chemical equation is \[ H_2S + 2H_2SO_4 \rightarrow 3S + 2H_2O \]. Let's break it down:

• Hydrogen sulfide has sulfur in the -2 oxidation state.
• As it reacts with sulfuric acid, hydrogen sulfide is oxidized to elemental sulfur, while sulfur in sulfuric acid is reduced from +6 to a lower oxidation state.

This reaction involves electron transfer, with hydrogen sulfide losing electrons and sulfuric acid gaining them. This transformation highlights how sulfur compounds can be interconverted through oxidation and reduction, making it a classic example of redox chemistry in action.