Problem 8 - A Complete Resource Book in Chemistry for JEE Main

Question

Thermite is a mixture of (a) \(\mathrm{Zn}+\mathrm{CaCO}_{3}\) (b) \(\mathrm{MgO}+\mathrm{Al}\) (c) \(\mathrm{Fe}_{3} \mathrm{O}_{4}+\mathrm{Al}\) (d) \(\mathrm{Zn}+\mathrm{P}_{2} \mathrm{O}_{5}\)

Step-by-Step Solution

Answer

The mixture is \(\text{Fe}_3\text{O}_4 + \text{Al}\).

Step 1: Understand Thermite Reaction

The thermite reaction involves a metal oxide and aluminum powder. It is a highly exothermic reaction where aluminum reduces the metal oxide to the metal, while aluminum oxide is formed.

Step 2: Identify Components of Thermite

We need to identify components that include a metal oxide and aluminum. Scanning through the options, only option (c) includes a metal oxide (\(\text{Fe}_3\text{O}_4\)) and aluminum (\(\text{Al}\)).

Step 3: Confirmation of Correct Mixture

Check if the reaction of \(\text{Fe}_3\text{O}_4\) and \(\text{Al}\) corresponds to the thermite reaction. \(\text{Fe}_3\text{O}_4\) is reduced to iron and aluminum forms aluminum oxide, matching the definition of a thermite reaction.

Key Concepts

Exothermic Reaction

An exothermic reaction is a type of chemical reaction that releases energy, usually in the form of heat. This release happens because the total energy needed to break the bonds of the reactants is less than the energy released when new bonds are formed in the products.
Such reactions often cause a temperature increase in the surrounding environment due to the energy that they emit.
Key features of exothermic reactions include:

• Heat Output: The most noticeable feature is the heat released during the reaction.
• Spontaneity: These reactions often occur spontaneously under the right conditions.
• Formation of Stable Products: Products formed tend to be more stable than the reactants.

The thermite reaction is a classic example of an exothermic reaction. Here, aluminum powder and metal oxide react to produce intense heat, which is why it is utilized in applications like welding.

Aluminum Reduction

Aluminum reduction is all about using aluminum as a reducing agent to remove oxygen from metal oxides.
This process, termed as reduction, converts the metal oxide into pure metal and aluminum gets oxidized to aluminum oxide.
This reaction type showcases aluminum's ability as a strong reducing agent, which is essential in various industrial chemical reactions.
Features of aluminum reduction in thermite reaction include:

• Efficient Reduction: Aluminum effectively strips oxygen from metal oxides, reducing them to metals.
• Energy Release: Such reductions are often coupled with significant energy output, explained by their exothermic nature.
• Formation of Aluminum Oxide: A stable white powder formed as a by-product in this reaction.

Metal Oxide

Metal oxides are compounds formed between metals and oxygen, displaying a range of properties depending on their metal components.
In the thermite reaction scenario, metal oxides like ext{Fe}_3 ext{O}_4 d are crucial because of their role as reactants that supply oxygen to facilitate the reduction process.
Important aspects of metal oxides in thermite reactions:

• Source of Oxygen: Metal oxides provide the oxygen required for aluminum to undergo oxidation.
• Forming Metals: Upon reduction by aluminum, the metal component is freed significantly.
• Diversity of Use: Various metal oxides can be used in thermite reactions, each providing different types of metal upon reduction.

For example, the combination of ext{Fe}_3 ext{O}_4 and aluminum in thermite reactions efficiently produces iron and aluminum oxide, illustrating the practical utility of different metal oxides.