Problem 18 - A Complete Resource Book in Chemistry for JEE Main

Question

The use of diamond as a gem depends on its (a) chemical inertness (b) hardness (c) purest form of carbon (d) high refractive index

Step-by-Step Solution

Answer

The use of diamond as a gem primarily depends on its high refractive index.

Step 1: Identify the Characteristics

We need to identify the properties of diamonds that affect their use as gems. The key characteristics to consider are chemical inertness, hardness, purity, and refractive index.

Step 2: Evaluate Chemical Inertness

Chemical inertness means that a material does not react easily with other substances. While important for durability, this property alone is not decisive for a diamond's use as a gem.

Step 3: Assess Hardness

Hardness refers to a material's resistance to being scratched. Diamonds are the hardest known natural material, which makes them highly resistant to scratching and helps maintain their luster over time.

Step 4: Consider Purity

Diamonds are a pure form of carbon, making them desirable for their clear, brilliant appearance. Purity enhances the aesthetic appeal but is not the sole characteristic for their use as gems.

Step 5: Evaluate Refractive Index

The refractive index measures how much light is bent when entering a material. Diamonds have a high refractive index, which gives them exceptional brilliance and sparkle, making them highly valued as gemstones.

Step 6: Determine Key Property

While several factors contribute to the value of diamonds, the high refractive index is particularly important for their use as gems, as it contributes to their brilliance and sparkle.

Key Concepts

Chemical Inertness

Diamonds are famous for their remarkable ability to resist chemical reactions. This characteristic, known as chemical inertness, stems from the strong covalent bonds between carbon atoms within the diamond's crystal lattice. In simpler terms, this means diamond does not easily react with other chemicals.

• Resists Corrosion: Unlike many other materials, diamonds do not corrode when exposed to typical solvents or acids.
• Maintains Appearance: Over time, diamonds retain their original beauty since they aren't affected by most chemical interactions.

However, as crucial as chemical inertness may be for durability, it doesn't greatly enhance a diamond's sparkle or beauty. While it helps in maintaining the gem's longevity, this property is not the primary reason diamonds are sought after as gems.

Hardness of Diamond

When it comes to hardness, diamonds reign supreme. Their position as the hardest natural material is cemented by their top ranking on the Mohs scale of mineral hardness. Hardness, in this context, refers to a diamond's ability to withstand scratching.

• Scratch Resistant: Diamonds can only be scratched by another diamond, making them exceptional for everyday wear.
• Long-Lasting: Because they retain their polish and smooth surface, diamonds maintain their lustrous appearance over years.

A diamond's hardness is one of the defining traits that contribute to its reputation and value. This durability makes diamonds an ideal choice for jewelry, ensuring they stay brilliant over a lifetime.

Refractive Index of Diamond

The brilliance of a diamond is predominantly due to its high refractive index. The refractive index is a measure of how much a substance can bend light. For diamonds, this property is exceptionally high, which means light entering the diamond creates a stunning interplay of sparkles and light.

• Exceptional Sparkle: With a refractive index of approximately 2.42, diamonds outshine many other gemstones.
• Intense Brilliance: Light entering a diamond undergoes total internal reflection, which amplifies its shine.
• Visual Appeal: This property creates the famous "fire" in diamonds, displaying brilliant flashes of color.

The high refractive index is the standout feature that distinguishes diamonds as the jewel of all gems, offering a visual spectacle that enchants viewers. It is this delightful sparkle and light interaction that make diamonds cherished and revered worldwide.