Question

White ZnO (s) becomes yellow upon heating due to

• A. Addition of electrons
• B. Creation of Frenkel defect
• C. Creation of F-centers
• D. All of the above

Answer 1

The correct option is C Creation of F-centers

On heating ZnO loses oxygen according to the following reaction.

$ZnO\to Z{n}^{2+}+\left(\frac{1}{2}\right)O_2+2e^{-}$

$Z{n}^{2+}$ ions and electrons move to interstitial sites and F-centres are created which impart yellow colour to ZnO(s).