Question

An ionic solid has $x\%$ Schottky defect and $y\%$ Frenkel defect. If theoretical density is $\rho$, the observed density is:

• A. $\rho \frac{x}{100}$
• B. $\rho (1-\frac{x}{100})$
• C. $\rho \frac{(x+y)}{100}$
• D. $\rho (1-\frac{x+y}{100})$

Answer 1

Answer: (B)

$\rho (1-\frac{x}{100})$

An ionic solid has $x\%$ Schottky defect and $y\%$ Frenkel defect.

If theoretical density is $\rho$, then the observed density is $\rho (1-\frac{x}{100})$.

This is because in Schottky defect cations and anions are removed in an equal equivalent from the unit cells and hence the density is decreased. But in Frenkel defect, the cations and anions are moved inside the interstitial space in the unit cell itself and therefore the density is unaltered.

Hence, option B is correct.