Problem 78 - A Complete Resource Book in Chemistry for JEE Main

Question

What is formed when aluminium trioxide reacts with sodium? (a) \(\mathrm{NaO}\) (b) \(\mathrm{NaO}_{2}\) (c) \(\mathrm{Na}_{2} \mathrm{O}\) (d) \(\mathrm{Na}_{2} \mathrm{O}_{2}\)

Step-by-Step Solution

Answer

The product formed is \(\mathrm{Na}_2\mathrm{O}\).

Step 1: Identify Reactants and Products

The reaction involves aluminium trioxide, which is represented as \( Al_2O_3 \) and sodium, represented as \( Na \). We need to identify the product formed from this reaction.

Step 2: Determine the Type of Reaction

Aluminium trioxide (\( Al_2O_3 \)) is an oxide that could potentially undergo a displacement reaction with sodium (\( Na \)), where sodium could replace aluminium to form a sodium oxide.

Step 3: Write the Balanced Equation

The balanced chemical equation for the reaction between aluminium trioxide and sodium is: \[ Al_2O_3 + 6Na \rightarrow 3Na_2O + 2Al \]. Here, aluminium is displaced, forming \( Na_2O \) and aluminium metal.

Step 4: Identify the Product

From the balanced equation, we can see that the product formed is \( Na_2O \), which is one of the possible answers given in the options.

Key Concepts

Displacement Reaction

In the world of chemistry, understanding different types of reactions is crucial, and one important category is the displacement reaction. This type of reaction occurs when an element reacts with a compound, displacing another element from it. In the case of our specific example involving aluminium trioxide ( Al_2O_3) and sodium (Na), sodium acts as the more reactive metal. As a result, it displaces aluminium (Al) from aluminium trioxide forming sodium oxide (Na_2O) and aluminium metal. Here, the general formula to remember is:

• An element + A compound -> A new compound + A displaced element

This type of reaction often occurs with metals and their oxides, particularly when a metal higher in the reactivity series displaces a less reactive metal from its compound.
Remember, the reactivity series is a handy chart that lists metals from most to least reactive, which helps determine whether a displacement reaction will occur.

Balancing Chemical Equations

Balancing chemical equations is one of the fundamental skills in chemistry. It ensures that we obey the Law of Conservation of Mass, meaning matter is not created or destroyed in a chemical reaction. Every atom that exists on the reactant side of the equation must also appear on the product side, allowing us to accurately predict the outcome of reactions.
In the equation provided for our exercise: \[ Al_2O_3 + 6Na \rightarrow 3Na_2O + 2Al \]each component must be balanced. This means there are:

• 2 Aluminium (Al) atoms on each side
• 3 Sodium (Na) atoms balanced as 6 on the left to correspond to 6 in the form of 3 Na_2O units on the right
• 3 Oxygen (O) atoms on both sides

Balancing such reactions requires practice. Start by balancing the most complex molecule and proceed step by step to ensure that each atom is accounted for on both sides of the equation.

Aluminium Trioxide

Aluminium trioxide, with the chemical formula \( Al_2O_3 \), is a compound composed of aluminium and oxygen. It is commonly found in nature as the mineral corundum, which is practically insoluble in water and highly stable, making it resistant to many chemical reactions.
This stability contributes to aluminium trioxide's importance in various industrial processes. For instance, it is used in the manufacture of aluminum metal through electrolysis in the Hall-Héroult process. Additionally, its hardness makes it valuable in producing abrasives and cutting tools due to the mineral’s characteristic attribute.
Understanding the properties of aluminium trioxide helps predict its behavior in reactions, such as its role in a displacement reaction where a more reactive metal like sodium might replace aluminium.

Sodium Oxide

Sodium oxide, often represented by the formula \( Na_2O \), is a simple yet significant chemical compound composed of sodium and oxygen. It forms as a ionic compound, which means it features strong ionic bonds between its constituent ions. This compound is typically produced in reactions where sodium metal reacts with oxygen.
In industrial settings, sodium oxide plays an important role in producing glass and ceramics, owing to its ability to form various silicates. Its chemical behavior must be understood for safety and efficacy in industrial applications.
Moreover, when sodium oxide is exposed to water, it reacts to form sodium hydroxide (NaOH). This reaction illustrates how sodium oxide functions as a basic oxide, reacting with acids to form salts and water, adhering to the typical behaviors of metal oxides.