Problem 72 - A Complete Resource Book in Chemistry for JEE Main

Question

Aluminium vessles should not be washed with materials containing washing soda because (a) washing soda reacts with aluminum to form insoluble aluminium oxide (b) washing soda reacts with aluminium to form soluble aluminate. (c) washing soda is expensive (d) washing soda is easily decomposed

Step-by-Step Solution

Answer

The correct reason is option (b): washing soda reacts with aluminium to form soluble aluminate.

Step 1: Identify the Chemical Reaction

Washing soda is chemically known as sodium carbonate (Na₂CO₃). When it reacts with aluminum (Al), it can form an aluminum aluminate. The general reaction is: \[ 2Al + 3Na_2CO_3 + 3H_2O \rightarrow 2Na[Al(OH)_4] + 3CO_2 \] Aluminum aluminate is soluble in water.

Step 2: Analyze Each Option

Review each option: - (a) suggests formation of insoluble aluminum oxide. However, Na₂CO₃ does not form aluminum oxide with aluminum. - (b) indicates formation of soluble aluminate when aluminum reacts with washing soda, which matches the chemical reaction. - (c) and (d) are unrelated to chemical reactivity and thus not applicable.

Step 3: Select the Correct Option

Based on the chemical reaction discussed, option (b), which states that 'washing soda reacts with aluminium to form soluble aluminate', is correct. This aligns with the given chemical equation showing the formation of sodium aluminate.

Key Concepts

Understanding the Sodium Carbonate Reaction

In the world of chemistry, sodium carbonate, often referred to as washing soda, is an important compound. It carries the chemical formula \( \text{Na}_2\text{CO}_3 \). When sodium carbonate reacts with other substances, new compounds form, which is fundamental to understanding chemical interactions.
Knowing how washing soda interacts with metals like aluminum is crucial. For instance, in a reaction with aluminum, sodium carbonate doesn't just sit idle. It actively participates in a chemical process that yields unexpected products.
Here’s the reaction broken down:

• Aluminum (Al) reacts with sodium carbonate \( (\text{Na}_2\text{CO}_3) \).
• Water \((\text{H}_2\text{O})\) is also part of this reaction.
• The result is sodium aluminate \( (\text{Na[Al(OH)}_4]) \) and carbon dioxide \((\text{CO}_2)\).

This demonstration of the sodium carbonate reaction reflects its significant role in forming compounds like sodium aluminate, illustrating the fascinating transformations that occur during chemical reactions.

Formation of Aluminum Aluminate

Aluminum aluminate is a compound that forms through specific reactions involving aluminum. This compound happens to be highly soluble in water, a property that distinguishes it from other aluminum-based compounds like aluminum oxide, which is insoluble.
The reaction producing aluminum aluminate relies on the combination of aluminum metal, washing soda (sodium carbonate), and water. In this scenario:

• Two aluminum atoms react with equal parts sodium carbonate and water.
• They produce two molecules of sodium aluminate \(\text{Na[Al(OH)}_4]\).
• Simultaneously, three molecules of carbon dioxide \(\text{CO}_2\) emerge as byproducts.

Understanding the solubility of aluminum aluminate in water is vital. It explains why aluminum vessels might degrade gradually when frequently exposed to washing soda. The formation of a soluble aluminate compound can lead to the progressive weakening of aluminum surfaces over time.

Basic Principles of Chemical Reactions with Metals

Metals have a significant role in the world of chemical reactions. Their ability to react, form new compounds, and change the properties of substances is fundamental in both scientific and everyday contexts. Metalloids, such as aluminum, engage in these reactions under specific conditions.
For example, aluminum is known for being reactive—particularly with bases like sodium carbonate. The general pattern of these reactions can be understood as follows:

• Metal atoms tend to lose electrons, which makes them reactive.
• When metals react with non-metal compounds, like sodium carbonate, they form metal complexes or salts.
• These reactions often produce gas byproducts, such as hydrogen or carbon dioxide, signifying a reaction has occurred.

In practical scenarios, understanding these principles helps in predicting and interpreting the outcomes of metal-based chemical reactions. It is important to consider how these interactions change material durability, affect chemical properties, and transform substances in both natural and industrial environments.