6. Explain:Zine oxide is white but it turns yellow on heatingbecomes h

1.	6. Explain:Zine oxide is white but it turns yellow on heatingbecomes highly conducting(a)(b)Cacl, will induce Schottky defect if added to Agcrystal.
Answer» a) Zinc oxide is an example of non stoichiometric defect under the category metal excess defect (excess cations occupying the interstitial site). In ZnO, Zn2+ions occupy the interstitial sites and electrons are trapped in the interstitial sites for the neutralization. Crystals that shows such type of defects are generally colored. Zinc oxide is white in color but on heating it turns into yellow because on heating it loses oxygen reversibly at high temperature. The reaction is as under:- ZnO → Zn2++ 1/2 O2+ 2e- b) Schottkey defect is the vacancy found in the crystal lattice of ionic compounds due to size difference in cations. Here, we know that Ca is a divalent cation and remains as Ca+2while silver is a univalent cation and remains as Ag+. So, when CaCl2is added to AgCl, then one Ca+2ion will replace two Ag+ions which will create a vacancy in place of one Ag+ion and so there will be the Schottkey defect in the compound.

6. Explain:Zine oxide is white but it turns yellow on heatingbecomes highly conducting(a)(b)Cacl, will induce Schottky defect if added to Agcrystal.

Answer»

a) Zinc oxide is an example of non stoichiometric defect under the category metal excess defect (excess cations occupying the interstitial site). In ZnO, Zn2+ions occupy the interstitial sites and electrons are trapped in the interstitial sites for the neutralization. Crystals that shows such type of defects are generally colored.

Zinc oxide is white in color but on heating it turns into yellow because on heating it loses oxygen reversibly at high temperature.

The reaction is as under:-

ZnO → Zn2++ 1/2 O2+ 2e-

b) Schottkey defect is the vacancy found in the crystal lattice of ionic compounds due to size difference in cations.

Here, we know that Ca is a divalent cation and remains as Ca+2while silver is a univalent cation and remains as Ag+.

So, when CaCl2is added to AgCl, then one Ca+2ion will replace two Ag+ions which will create a vacancy in place of one Ag+ion and so there will be the Schottkey defect in the compound.

6. Explain:Zine oxide is white but it turns yellow on heatingbecomes highly conducting(a)(b)Cacl, will induce Schottky defect if added to Agcrystal.

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