question_answer 90)

  Which of the following statements are not true? (a) Vacancy defect results in a decrease in the density of the substance (b) Interstitial defects results in an increase in the density of the substance (c) Impurity defect has no effect on the density of the substance (d) Frenkel defect results in an increase in the density of the substance

Answer:

                  (c, d) Statements (c) and (d) can be correctly written as (c) lmpurity defect changes the density of substance as impurity has different density than the ion present on perfect crystal. e.g... When SrCl2 is added to the NaCI crystal it causes impurity defect. (d) Frenkel defect results neither decrease nor increase in density of substance.