Question

Identify the correct statement about properties of interstitial compounds.

• A. Melting point of these compounds is lower than parent metal.
• B. Densities of these compounds are higher than parent metal.
• C. Chemical properties of interstitial compounds are different than parent metal.
• D. Metallic carbides are chemically inert.

Hint:

Interstitial compounds lock up the lattice structure, which drastically boosts hardness and melting points while making the overall material highly resistant to chemical attacks (inert)!

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
We need to analyze the characteristic physical and chemical trends of interstitial compounds (formed when small atoms like H, C, or N trap inside the crystal lattices of transition metals) and pick the true statement.

Step 2: Detailed Explanation:
Interstitial compounds exhibit distinct modifications due to the locking of metal lattice slippage planes by non-metal impurities:

• Melting Point: They possess very high melting points, which are significantly higher than those of the pure parent metals due to increased structural bonding stability. This makes statement (A) false.

• Chemical Reactivity: The chemical properties of interstitial compounds remain largely matching and similar to the host parent metal rather than changing entirely, making statement (C) false.

• Inertness: Due to the filling of interstitial voids, these compounds become structurally dense and remarkably less reactive. Transition metal carbides and borides exhibit extreme hardness resembling diamond and are exceptionally chemically unreactive or inert. This makes statement (D) completely true.


Step 3: Final Answer: The correct statement is that metallic carbides are chemically inert, corresponding to option (D).