Question

In which of the following reactions $ \text{B}_2\text{O}_3 $ is not formed?

• A. Acidifying an aqueous solution of $ \text{Na}_2\text{B}_4\text{O}_7 $
• B. Heating of Boron in air
• C. Burning of $ \text{B}_2\text{H}_6 $ in oxygen
• D. On heating $ \text{H}_3\text{BO}_3 $ above $ 370 \, \text{K} $

Hint:

To determine whether $ \text{B}_2\text{O}_3 $ is formed: 1. Identify reactions involving boron or its compounds. 2. Check if the reaction produces $ \text{B}_2\text{O}_3 $ as a product.

Answer 1

The Correct Option is A

\textbf{Step 1: Understand the Formation of $ \text{B_2\text{O}_3 $}}
$ \text{B}_2\text{O}_3 $ is a common oxide of boron and is typically formed when boron or its compounds react with oxygen under certain conditions. Let's analyze each option to determine whether $ \text{B}_2\text{O}_3 $ is formed. Step 2: Analyze Each Option
Option (1): Acidifying an aqueous solution of $ \text{Na}_2\text{B}_4\text{O}_7 $ $ \text{Na}_2\text{B}_4\text{O}_7 $ is sodium tetraborate, also known as borax.
When acidified, the reaction produces boric acid ($ \text{H}_3\text{BO}_3 $), not $ \text{B}_2\text{O}_3 $. The reaction is: $$ \text{Na}_2\text{B}_4\text{O}_7 + 2\text{HCl} \rightarrow 4\text{H}_3\text{BO}_3 + 2\text{NaCl} $$ No $ \text{B}_2\text{O}_3 $ is formed. Option (2): Heating of Boron in air
When boron is heated in air, it reacts with oxygen to form $ \text{B}_2\text{O}_3 $. The reaction is: $$ 4\text{B} + 3\text{O}_2 \rightarrow 2\text{B}_2\text{O}_3 $$ $ \text{B}_2\text{O}_3 $ is formed. Option (3): Burning of $ \text{B}_2\text{H}_6 $ in oxygen
$ \text{B}_2\text{H}_6 $ (diborane) burns in oxygen to form $ \text{B}_2\text{O}_3 $ and water. The reaction is: $$ \text{B}_2\text{H}_6 + 3\text{O}_2 \rightarrow \text{B}_2\text{O}_3 + 3\text{H}_2\text{O} $$ $ \text{B}_2\text{O}_3 $ is formed. Option (4): On heating $ \text{H}_3\text{BO}_3 $ above $ 370 \, \text{K} $ When boric acid ($ \text{H}_3\text{BO}_3 $) is heated above $ 370 \, \text{K} $, it decomposes to form $ \text{B}_2\text{O}_3 $ and water vapor. The reaction is:
$$ 2\text{H}_3\text{BO}_3 \xrightarrow{\text{above } 370 \, \text{K}} \text{B}_2\text{O}_3 + 3\text{H}_2\text{O} $$ $ \text{B}_2\text{O}_3 $ is formed. Step 3: Identify the Correct Option
From the analysis, Option (1) is the only process where $ \text{B}_2\text{O}_3 $ is not formed.