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Question
Why is FeO (s) not formed in stoichiometric composition?
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Solution
In the crystals of FeO, some of the Fe2+ cations are replaced by Fe3+ ions. Three Fe2+ ions are replaced by two Fe3+ ions to make up for the loss of positive charge. Eventually there would be less amount of metal as compared to stoichiometric proportion.
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RELATED QUESTIONS
Explain the following term with suitable examples:
Frenkel defect
Explain the following term with a suitable example:
Interstitials
Examine the given defective crystal:
Answer the following questions :
(i) What type of stoichiometric defect is shown by the crystal?
(ii) How is the density of the crystal affected by this defect?
(iii) What type of ionic substances show such defect?
non-stoichiometric defects?
Out of NaCl and AgCl, which one shows Frenkel defect and why?
Defect shown by non-ionic solids is ____________.
Defects in solids can be studied using
The radius of Cs+ is 169 pm and Cl− is 181 pm. The radius ratio is ____________.
The following diagram shows:
Which is not correct about the Schottky defects?
Assertion: No compound has both Schottky and Frenkel defects.
Reason: Both defects change the density of the solid.
Assertion: Due to Frenkel defect, there is no effect on the density of the crystalline solid.
Reason: In Frenkel defect, no cation or anion leaves the crystal.
Silver halides generally show:
Which of the following point defects are shown by AgBr(s) crystals?
- Schottky defect
- Frenkel defect
- Metal excess defect
- Metal deficiency defect
Which of the following statements are not true?
(i) Vacancy defect results in a decrease in the density of the substance.
(ii) Interstitial defects results in an increase in the density of the substance.
(iii) Impurity defect has no effect on the density of the substance.
(iv) Frankel defect results in an increase in the density of the substance.
Frenkel defect is also known as:
(i) stoichiometric defect
(ii) dislocation defect
(iii) impurity defect
(iv) non-stoichiometric defect
Match the defects given in Column I with the statements in given Column II.
| Column I | Column II |
| (i) Simple vacancy defect | (a) shown by non-ionic solids and increases density of the solid. |
| (ii) Simple interstitial defect | (b) shown by ionic solids and decreases density of the solid. |
| (iii) Frenkel defect | (c) shown by non ionic solids and density of the solid decreases. |
| (iv) Schottky defect | (d) shown by ionic solids and density of the solid remains the same. |
Given below are two statements, one is labelled as Assertion (A) and the other is labelled as Reason (R):
Assertion: In any ionic solid (MX) with Schottky defects, the number of positive and negative ions are same.
Reason: Equal number of cation and anion vacancies are present.
