Problem 131 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following compounds contain boron? (a) Colemanite (b) Kernite (c) Borax (d) Cristoballite

Step-by-Step Solution

Answer

Colemanite, Kernite, and Borax contain boron.

Step 1: Understanding the Question

Our goal is to identify which among the given compounds contains the element boron. These compounds are often found in chemistry, specifically as mineral sources of boron.

Step 2: Analyzing Options

Let's briefly analyze each option in terms of their known chemical composition: - **Colemanite** is a borate mineral, which indicates it contains boron. - **Kernite**, also known as rasorite, is another borate mineral containing boron. - **Borax** is a well-known boron compound used in various applications, scientifically called sodium borate. - **Cristoballite** is a form of silica (SiO₂) and does not contain boron.

Step 3: Filtering the Correct Answers

Based on the analysis above, the compounds containing boron are: - Colemanite - Kernite - Borax Cristoballite, being a form of silica, does not contain boron.

Key Concepts

Minerals containing Boron

Boron is a fascinating element that is typically found in certain minerals. These minerals are naturally occurring, inorganic substances that often contain valuable compounds for various industrial and commercial applications. Some minerals are especially rich in boron and serve as primary sources for extracting this element.
Boron is usually present in the form of borate minerals, which are crystals containing both boron and oxygen atoms in their structure. The ability to form such unique minerals makes boron particularly important in the fields of chemistry and geology. Understanding the key minerals that contain boron helps in identifying their applications and the benefits they offer. Let's take a closer look into how boron is present in some significant minerals.

Borate Minerals

Borate minerals are a special class of minerals that include boron within their chemical structure. These minerals are highly valued due to their wide range of uses, from glass production to detergents and beyond.
Let's delve into a few notable borate minerals:

• **Colemanite**: This is a calcium borate hydrate mineral, recognized for its occurrence in evaporite deposits of boron. It is mined as an important source of boron used in various industries, including ceramics and agriculture.
• **Kernite**: Also known as rasorite, kernite is another important borate. It is a hydrate of sodium borate and is primarily found in the U.S., being of significant economic and industrial value for boron extraction.
• **Borax**: Scientifically known as sodium borate, borax is perhaps the most well-known borate mineral. It has a variety of household and industrial applications, from cleaning agents to fire retardants.

Characteristics of borate minerals, like their solubility in water and their efficacy in glass manufacturing, make them a valuable resource in numerous fields.

Chemical Composition

Understanding the chemical composition of minerals is key to knowing their potential uses and properties. In the context of borate minerals, the composition primarily involves boron atoms bonded with oxygen, often in conjunction with other elements such as sodium or calcium.
For example:

• **Colemanite**: Chemically, this mineral is represented as CaB\(_3\)O\(_4\)(OH)\(_3\)·H\(_2\)O, where calcium plays a crucial part in its structure alongside boron.
• **Kernite**: This mineral's composition can be written as Na\( _2\)B\(_4\)O\(_ .7\)4H\(_2\)O. The combination of sodium and boron provides its unique properties.
• **Borax**: It has a chemical composition of Na\(_2\)B\(_4\)O\(_7\)·10H\(_2\)O, demonstrating again the presence of sodium and boron.

These compositions reveal how boron interacts with other elements and forms stable, high-utility compounds. This understanding aids in developing processes for mining and utilizing these minerals efficiently across various industries.