Which of the following statements regarding interstitial compounds is incorrect?

Which of the following statements regarding interstitial compounds is incorrect? +

Correct Answer

Incorrect statement: Interstitial compounds are always non-stoichiometric.

Detailed Explanation

Interstitial compounds are formed when small atoms such as H, B, C or N occupy the interstitial spaces (holes) in the crystal lattice of transition metals. Common examples include:

Fe₃C   |   TiC   |   VN   |   Fe₄N

Their important characteristics are:

• They are generally hard and rigid.
• They often have high melting points.
• They generally retain the metallic conductivity of the parent metal.
• They are usually formed by small atoms occupying interstitial sites in a metal lattice.
• They may be non-stoichiometric, but they are not necessarily always non-stoichiometric.

Therefore, saying that all interstitial compounds are necessarily non-stoichiometric is incorrect.

Why are they called Interstitial Compounds?

The small atoms do not normally replace metal atoms in the crystal lattice. Instead, they occupy the empty spaces between the metal atoms.

Metal lattice + small atom in interstitial site → Interstitial compound

For example, carbon atoms can occupy the spaces in the iron lattice to form iron carbide.

JEE / NEET Quick Revision

Interstitial compounds → small atoms in lattice holes → hard + high m.p. + metallic conductivity → often non-stoichiometric, but not always.

30 Related MCQs with Solutions

1. Interstitial compounds are formed when small atoms occupy:

A. Substitutional sites only

B. Interstitial sites

C. Nuclei of metal atoms

D. Valence shells only

Answer: B. Interstitial sites

2. Which of the following atoms commonly forms interstitial compounds?

A. Na

B. K

C. C

D. Cs

Answer: C. Carbon

3. Interstitial compounds are mainly associated with:

A. Alkali metals

B. Transition metals

C. Noble gases

D. Halogens

Answer: B. Transition metals

4. Which is an example of an interstitial compound?

A. NaCl

B. TiC

C. H₂O

D. CO₂

Answer: B. TiC

5. Interstitial compounds are generally:

A. Soft

B. Hard

C. Gaseous

D. Volatile liquids

Answer: B. Hard

6. Interstitial compounds generally have:

A. Very low melting points

B. High melting points

C. No melting point

D. Melting points below room temperature

Answer: B. High melting points

7. Which property is usually retained by interstitial compounds?

A. Metallic conductivity

B. Molecular volatility

C. Ionic conductivity only

D. Gas-like behaviour

Answer: A. Metallic conductivity

8. Which statement is incorrect?

A. Small atoms occupy lattice holes

B. They are generally hard

C. They always have fixed stoichiometry

D. They can retain metallic character

Answer: C.
Interstitial compounds can often show variable composition.

9. Which element can occupy interstitial positions in transition-metal lattices?

A. Hydrogen

B. Carbon

C. Nitrogen

D. All of these

Answer: D. All of these

10. The small atoms in interstitial compounds are generally:

A. Larger than metal atoms

B. Smaller than metal atoms

C. Equal in size to metal atoms

D. Always noble gases

Answer: B. Smaller than metal atoms

11. Which compound is associated with iron and carbon?

A. FeCl₃

B. Fe₃C

C. FeSO₄

D. Fe(NO₃)₃

Answer: B. Fe₃C

12. Which of the following is a carbide-type interstitial compound?

A. TiC

B. NaCl

C. MgO

D. CaCO₃

Answer: A. TiC

13. Interstitial compounds are generally formed by:

A. Large non-metals entering lattice sites

B. Small atoms entering lattice holes

C. Complete replacement of metal atoms

D. Noble gases entering the nucleus

Answer: B

14. Which is NOT a typical property of interstitial compounds?

A. High hardness

B. High melting point

C. Metallic conductivity

D. High volatility

Answer: D. High volatility

15. Interstitial compounds may be:

A. Only stoichiometric

B. Only non-stoichiometric

C. Stoichiometric or non-stoichiometric

D. Always molecular

Answer: C

16. The term "interstitial" refers to:

A. Surface of a crystal

B. Space between atoms in a lattice

C. Nucleus of an atom

D. Electron cloud

Answer: B

17. Which element is particularly small and can enter metal lattice holes?

A. H

B. Cs

C. Rb

D. Ba

Answer: A. Hydrogen

18. Interstitial compounds are usually:

A. Non-metallic insulators

B. Metallic or metal-like in conductivity

C. Molecular gases

D. Ionic liquids

Answer: B

19. Which statement about stoichiometry is correct?

A. All interstitial compounds must be non-stoichiometric

B. Some interstitial compounds have definite stoichiometry

C. None have definite composition

D. Stoichiometry is impossible

Answer: B

20. Which pair contains interstitial compounds?

A. TiC and VN

B. NaCl and KBr

C. H₂O and NH₃

D. CO₂ and SO₂

Answer: A. TiC and VN

21. Interstitial atoms mainly cause:

A. Weakening of the metallic lattice

B. Distortion and strengthening of the lattice

C. Complete destruction of lattice

D. Formation of a gas

Answer: B

22. Which is an important industrial feature of many interstitial compounds?

A. High hardness

B. Extreme volatility

C. Low thermal stability

D. Low melting point

Answer: A. High hardness

23. Carbon in iron lattice can form:

A. Fe₃C

B. FeCl₃

C. FeO₄

D. Fe(NO₃)₂

Answer: A. Fe₃C

24. Which small atoms are commonly involved in interstitial compounds?

A. H, B, C, N

B. Na, K, Rb, Cs

C. Cl, Br, I, At

D. Xe, Kr, Ar, Ne

Answer: A

25. Which statement is true?

A. Interstitial compounds are always ionic

B. Interstitial compounds are generally associated with metallic lattices

C. Interstitial compounds are always molecular

D. They contain no metals

Answer: B

26. Which property results from strong interaction between the interstitial atom and metal lattice?

A. Increased hardness

B. Increased volatility

C. Gas formation

D. Loss of all conductivity

Answer: A

27. Which statement is incorrect regarding interstitial compounds?

A. Small atoms occupy lattice holes

B. They are generally hard

C. They are always non-stoichiometric

D. They may have high melting points

Answer: C. They are always non-stoichiometric

28. VN is an example of an interstitial compound involving:

A. Vanadium and nitrogen

B. Vanadium and sodium

C. Vanadium and neon

D. Vanadium and chlorine

Answer: A. Vanadium and nitrogen

29. The electrical conductivity of many interstitial compounds is:

A. Metallic

B. Always zero

C. Only ionic

D. Molecular

Answer: A. Metallic

30. The best description of interstitial compounds is:

A. Small atoms occupy interstitial sites of a metal lattice

B. Large atoms replace all metal atoms

C. Only non-metals form them

D. They are always gaseous

Answer: A

Advertisement