Problem 16 - A Complete Resource Book in Chemistry for JEE Main

Question

When \(\mathrm{K}_{2} \mathrm{O}\) is added to water, the solution is basic because it contains a significant concentration of (a) \(\mathrm{OH}^{-}\) (b) \(\mathrm{K}^{+}\) (c) \(\mathrm{O}^{3-}\) (d) \(\mathrm{O}_{2}^{2-}\)

Step-by-Step Solution

Answer

The solution is basic because it contains \\(\text{OH}^-\\).

Step 1: Understand the Reaction

When potassium oxide (\(\text{K}_2\text{O}\)) is added to water, it reacts to form a solution. We need to write the chemical equation for this reaction to determine which ions are produced.

Step 2: Write the Chemical Equation

The chemical reaction when \(\text{K}_2\text{O}\) is added to water is:\[ \text{K}_2\text{O} + \text{H}_2\text{O} \rightarrow 2\text{K}^+ + 2\text{OH}^- \]This shows that potassium ions (\(\text{K}^+\)) and hydroxide ions (\(\text{OH}^-\)) are formed in the solution.

Step 3: Identify the Ion Responsible for Basicity

Now, observe the ions formed. A solution is basic if there is a significant concentration of hydroxide ions \(\text{OH}^-\). Here, \(\text{OH}^-\) ions are produced in the reaction, making the solution basic.

Key Concepts

Potassium Oxide Reaction with Water

When potassium oxide, known chemically as \(\text{K}_2\text{O}\), is introduced to water, an interesting chemical transformation occurs. This oxide of potassium dissolves and reacts with water to produce potassium ions \(\text{K}^+\) and hydroxide ions \(\text{OH}^-\). The balanced chemical equation representing this reaction is written as: \[ \text{K}_2\text{O} + \text{H}_2\text{O} \rightarrow 2\text{K}^+ + 2\text{OH}^- \] This equation tells us about the products of the reaction and emphasizes the generation of hydroxide ions, which is crucial for understanding the resulting properties of the solution. Potassium oxide is known as a basic oxide, meaning it generally reacts with water to form a basic solution. This is largely due to the presence of those generated \(\text{OH}^-\) ions.

Chemical Reactions with Water

Chemical reactions involving water are fundamental and form the basis of many processes both in nature and in industrial applications. When a compound reacts with water, it can either donate or accept protons, or it can dissociate into ions. The reaction includes several important types:

• Acidic oxides, which produce H\(^+\) ions in water, making an acidic solution.
• Basic oxides, like \(\text{K}_2\text{O}\), that release \(\text{OH}^-\) ions in water, making the solution basic.
• Amphoteric oxides that can behave as either acids or bases depending on the reacting substances.

These reactions showcase the versatility of oxides reacting with water, depending on their nature, and play a vital role in various aqueous systems.

Hydroxide Ions and Basicity

The concept of basicity is intertwined closely with the presence of hydroxide ions in a solution. A basic solution is characterized by its ability to accept protons, which is manifested through the generation of \(\text{OH}^-\). In water, hydroxide ions increase the pH of the solution, thereby making it basic or alkaline. The link between \(\text{OH}^-\) ions and basicity is evident in reactions like those where substances like potassium oxide dissolve in water.

• These hydroxide ions are crucial for many chemical processes, such as neutralization reactions.
• In industrial and laboratory applications, they are responsible for alkalinity, assisting in cleaning agents and chemical synthesis.

Understanding how the quantity of \(\text{OH}^-\) ions affects pH helps in controlling reactions and designing solutions with desired properties.