| Directions: (Q. 21 to 25) |
| Case V: Read the passage given below and answer the following questions from 21 to 25. |
| In an ideal crystal, there must be regular repeating arrangement of the constituting particles and its entropy must be zero at absolute zero temperature. However, it is impossible to obtain an ideal crystal and it suffers from certain defects called imperfections. In pure crystal, these defects arises either due to disorder or dislocation of the constituting particles from their normal positions or due to the movement of the particles even at absolute zero temperature. |
| Such defects increase with rise in temperature. In addition to this, certain defects arise due to the presence of some impurities. Such defects not only modify the existing properties of the crystalline solids but also impart certain new characteristics to them. |
A) cationic vacancies equal to number of \[C{{d}^{2+}}\]ions incorporated
B) cationic vacancies equal to double the number of \[C{{d}^{2+}}\] ions
C) anionic vacancies
D) neither cationic nor anionic vacancies.
Correct Answer: A
Solution :
In the crystallisation, some \[A{{g}^{+}}\] ions will get replaced by \[C{{d}^{2+}}\] ions and each \[C{{d}^{2+}}\] ion replaces two \[A{{g}^{+}}\]ions so as to maintain electrical neutrality. Thus, the cation vacancies will be the same as the number of \[C{{d}^{2+}}\]ions incorporated.
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