ZnO shows yellow colour on heating due to: | vedclass

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Question

(D) $ZnO$ is white at room temperature. On heating,it loses oxygen and turns yellow due to the formation of metal excess defect. The reaction is: $ZnO

Vedclass · Accepted Answer

Metal excess defect due to $F$-centres

Vedclass · Answer

(D) $ZnO$ is white at room temperature. On heating,it loses oxygen and turns yellow due to the formation of metal excess defect. The reaction is: $ZnO \xrightarrow{\Delta} Zn^{2+} + \frac{1}{2}O_2 + 2e^-$. The excess $Zn^{2+}$ ions move to interstitial sites and the electrons move to neighboring interstitial sites to maintain electrical neutrality. These trapped electrons in the interstitial sites behave like $F$-centres,which absorb light from the visible region and impart a yellow colour to the crystal.

$ZnO$ shows yellow colour on heating due to:

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