Problem 33 - A Complete Resource Book in Chemistry for JEE Main

Question

Sodium metal reacts with \(\mathrm{Al}_{2} \mathrm{O}_{3}\) at high temperature to give a sodium compound X.X reacts with carbon dioxide in water to form Y.Y is ...... (a) \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) (b) \(\mathrm{Na}_{2} \mathrm{O}_{2}\) (c) \(\mathrm{NaAlO}_{2}\) (d) \(\mathrm{Na}_{2} \mathrm{O}\)

Step-by-Step Solution

Answer

Y is \( \mathrm{Na}_{2} \mathrm{CO}_{3} \), i.e., option (a).

Step 1: Sodium Reacts with Aluminum Oxide

Sodium (Na) reacts with aluminum oxide \( \mathrm{Al}_{2} \mathrm{O}_{3} \) to form sodium aluminate (\( \mathrm{NaAlO}_{2} \)). The balanced chemical equation for this reaction is: \( 6 \mathrm{Na} + \mathrm{Al}_{2} \mathrm{O}_{3} \rightarrow 2 \mathrm{NaAlO}_{2} + 3 \mathrm{Na} \). This means compound X is sodium aluminate \( \mathrm{NaAlO}_{2} \)).

Step 2: Formation of Compound Y

Compound X (\( \mathrm{NaAlO}_{2} \)) reacts with carbon dioxide and water. The reaction of \( \mathrm{NaAlO}_{2} \) with \( \mathrm{CO}_2 \) and \( \mathrm{H}_2\mathrm{O} \) typically results in the formation of sodium carbonate \( \mathrm{Na}_{2} \mathrm{CO}_{3} \) and aluminum hydroxide \( \mathrm{Al(OH)}_{3} \) as by-products. The equation can be simplified as: \( 2\mathrm{NaAlO}_{2} + \mathrm{CO}_{2} + 2\mathrm{H}_{2}\mathrm{O} \rightarrow 2\mathrm{Al(OH)}_{3} + \mathrm{Na}_{2} \mathrm{CO}_{3} \). Hence, compound Y is \( \mathrm{Na}_{2} \mathrm{CO}_{3} \).

Step 3: Identify the Product Y

From the above reactions, \( \mathrm{Na}_{2} \mathrm{CO}_{3} \) is the compound formed after \( \mathrm{NaAlO}_{2} \) reacts with \( \mathrm{CO}_{2} \) and water. Thus, the correct answer is \( \mathrm{Na}_{2} \mathrm{CO}_{3} \) which matches option (a).

Key Concepts

Understanding Chemical Reactions

Chemical reactions involve the transformation of substances through a process where atomic bonds are broken, formed, or rearranged. Chemical reactions are essential for processes in our daily lives and in industry, bringing about changes in substances called reactants to produce new substances called products.

When sodium reacts with aluminum oxide (\( \mathrm{Al}_{2} \mathrm{O}_{3} \)), a new product, sodium aluminate (\( \mathrm{NaAlO}_{2} \)), is formed. This reaction is a type of chemical synthesis, where simple reactants form a more complex product. Chemical equations represent these changes, showing the reactants on the left side of an arrow and the products on the right. Understanding chemical reactions requires recognizing how these transformations occur and being able to predict the products based on known reactions and patterns.

Exploring Sodium Carbonate

Sodium carbonate, often known as washing soda or soda ash, is a white, water-soluble salt with the chemical formula \( \mathrm{Na}_{2} \mathrm{CO}_{3} \). It has many applications such as in glass making, as a water softener in laundering, and in chemical manufacturing.

In the context of sodium aluminate reactions, when sodium aluminate (\( \mathrm{NaAlO}_{2} \)) comes in contact with carbon dioxide and water, it decomposes into sodium carbonate and aluminum hydroxide. This makes \( \mathrm{Na}_{2} \mathrm{CO}_{3} \) a key product to identify when dealing with chemical reactions involving sodium compounds interacting with carbon-based or acidic substances. It's important to grasp the role of sodium carbonate as it significantly contributes to the overall balance and outcome of reactions.

The Importance of a Balanced Chemical Equation

Balancing chemical equations is crucial because it ensures that the same amount of each element is present on both sides of the equation, aligning with the Law of Conservation of Mass. This law states that mass cannot be created or destroyed in a chemical reaction.

For the reaction involving sodium and aluminum oxide producing sodium aluminate, the equation must depict an equal number of each type of atom before and after the reaction: \[ 6 \mathrm{Na} + \mathrm{Al}_{2} \mathrm{O}_{3} \rightarrow 2 \mathrm{NaAlO}_{2} + 3 \mathrm{Na} \].

Balancing helps in accurately predicting the outcomes of reactions and is essential for quantitative calculations in chemistry. It ensures proper proportioning of reactants and aids in scaling reactions for practical applications.

Understanding Sodium Hydroxide

Sodium hydroxide is a highly caustic substance, commonly known as lye or caustic soda, with the chemical formula \( \mathrm{NaOH} \). It is colloquially famous for its use in soap making, paper production, and chemical manufacturing.

In the context of the reaction discussed, although sodium hydroxide is not directly involved, its structure helps us understand related compounds like sodium aluminate and sodium carbonate. Sodium hydroxide forms the basis of understanding basic chemical behaviors in sodium compounds, especially those interacting with water.

Mechanism of Carbon Dioxide Reaction

The reaction of carbon dioxide with other substances is a common chemical process, especially in the formation of carbonates. When carbon dioxide reacts with water, it forms carbonic acid, which readily reacts with sodium-based substances, leading to the formation of sodium carbonate.

In the reaction chain described, carbon dioxide reacts with water and sodium aluminate to form sodium carbonate and aluminum hydroxide. \[ 2\mathrm{NaAlO}_{2} + \mathrm{CO}_{2} + 2\mathrm{H}_{2}\mathrm{O} \rightarrow 2\mathrm{Al(OH)}_{3} + \mathrm{Na}_{2} \mathrm{CO}_{3} \].

This illustrates how carbon dioxide, a simple and abundant molecule in the atmosphere, can facilitate significant chemical changes, forming essential compounds like sodium carbonate. Comprehending carbon dioxide reactions broadens our understanding of not only chemistry but also natural processes such as gas exchange and mineral formation.