Question

Assertion: Both Frenkel and Schottky defects are stoichiometric defects.
Reason: Both defects change the density of the crystalline solid.
(A) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
(B) Both Assertion and Reason are correct and but Reason is not the correct explanation for Assertion
(C) Assertion is correct but Reason is incorrect
(D) both Assertion and Reason are incorrect

Answer 1

Many small crystals formed solids. The defect in solids due to the fast or moderate rate of formation of crystals during the process of crystallization. Defects are generally defined as the irregularities in the arrangement of constituent particles and it may be the point or line defect based on the irregular rearrangement.

Complete answer:
According to the third law of thermodynamics, at an absolute temperature of 0 K, any substance will be a perfect crystal but increasing the temperature creates defects in solids. These defects in solid are classified into three types:
(1) Stoichiometric defects
(2) Non-stoichiometric defects
(3) Impurity defects
Stoichiometric defects: This defect will be observed in which the stoichiometric of the compound remains the same as shown by their formula and this defect is also called intrinsic or thermodynamic defects. For ionic solids, these are further classified into Frenkel and Schottky defects. So, both Frankel and Schottky defects are stoichiometric defects. Hence, the Assertion is true. When some of the ions are occupied by the interstitial spaces leaving lattice space raises Frenkel defects and is observed in where cations are smaller than anions due to there is no change in the crystal. When an equal number of cations and anions are missing from the lattice then arises Schottky defects. Both cations and anions are the same because the density of crystal decreases in ionic compounds of higher coordination numbers. So, Schottky defects only change the density of crystal but not the Frenkel defect. Hence, Assertion is true and Reason is incorrect.

The correct option is C.

Note: Mostly due to misalignment of ions or the presence of vacancies along a line are line defects. An edge dislocation appears when lines of ions are missing in an otherwise perfect array of ions and it is responsible for the ductility and malleability. The edge location movement involves the hammering and stretching of materials.