Question

The incorrect statement about the imperfections in solids is:

• A. Schottky defect decreases the density of the substance.
• B. Interstitial defect increases the density of the substance.
• C. Frenkel defect does not alter the density of the substance.
• D. Vacancy defect increases the density of the substance.

Answer 1

The Correct Option is D

To determine the incorrect statement regarding imperfections in solids, let's explore each option:

1. Schottky defect decreases the density of the substance.

   This statement is true. A Schottky defect occurs when an equal number of cations and anions are missing from their lattice sites. This causes a reduction in the mass of the crystal without a corresponding decrease in volume, thus decreasing the density of the substance.

2. Interstitial defect increases the density of the substance.

   This statement is true. An interstitial defect occurs when extra atoms are inserted into the interstitial sites of the crystal lattice. The addition of atoms increases the overall mass of the solid without a significant increase in volume, thus increasing the density.

3. Frenkel defect does not alter the density of the substance.

   This statement is true. In a Frenkel defect, atoms or ions are displaced from their original lattice points and occupy interstitial positions. Since no ion is lost from the lattice, the overall density remains unchanged.

4. Vacancy defect increases the density of the substance.

   This statement is incorrect. A vacancy defect arises when atoms are missing from their lattice sites. This leads to a reduction in mass without a reduction in volume, causing the density to decrease. Therefore, this statement is the incorrect one.

Upon analyzing these defects, it is clear that the incorrect statement is: "Vacancy defect increases the density of the substance." In reality, a vacancy defect decreases the density of the substance.