AIIMS 2005 Chemistry Metallurgy Assertion Reason Question

To analyze the question, we need to evaluate both the assertion and the reason provided:

Assertion:

Extraction of iron metal from iron oxide ore is carried out by heating with coke.

This statement is indeed true. The extraction of iron from iron oxide ores, particularly hematite ($Fe_2O_3$), is commonly performed using coke (a form of carbon) in a blast furnace. The process involves heating the ore with coke, where coke serves as both a fuel and a reducing agent.

Reason:

The reaction $Fe_2O_3(s) \rightarrow Fe(s) + \frac{3}{2} O_2(g)$ is a spontaneous process.

This statement is false. The reaction presented is not the correct representation of the reduction of iron oxide. The actual reaction that occurs during the extraction involves the reduction of iron oxide by carbon (from coke), which can be represented as:

$$Fe_2O_3(s) + 3C(s) \rightarrow 2Fe(s) + 3CO(g)$$

In this reaction, carbon monoxide ($CO$) is produced, and it is this $CO$ that actually reduces iron(III) oxide to iron metal. Moreover, the reaction as stated in the reason does not indicate a spontaneous process because the formation of $O_2(g)$ suggests that oxygen is being released, which contradicts the reduction process occurring in the furnace.

Conclusion:

• Assertion is true: The extraction of iron does involve heating with coke.
• Reason is false: The reaction described does not occur as stated, and it is not spontaneous in the context provided.

Thus, the correct answer is D: If both assertion and reason are false.

Why Other Options Are Incorrect:

• Option A: Incorrect, because while the assertion is true, the reason is false. Therefore, it cannot be the correct explanation.
• Option B: Incorrect for the same reason as Option A. The reason does not accurately explain the assertion.
• Option C: Incorrect, as it states that the assertion is true but the reason is false, which does not fit the criteria of the options provided.

Key Concepts:

1. Metallurgy: The science and technology of metals, which includes the extraction of metals from their ores.
2. Reduction Reaction: A chemical reaction that involves the gain of electrons or a decrease in oxidation state. In the case of iron extraction, $Fe_2O_3$ is reduced to $Fe$ by carbon.
3. Spontaneity: A process is spontaneous if it can occur without being driven by an external force. This is often assessed using Gibbs free energy ($\Delta G$) where a negative $\Delta G$ indicates spontaneity.

In summary, the correct choice is D, because the assertion is true, while the reason is false due to an incorrect representation of the reaction and its spontaneity.