Question

Assertion: On heating $ZnO$ , it acquires yellow colour.
Reason: $ Zn^{+2}$ generated on heating $ZnO$ remains in excess and move to interstitial sites and electrons to neighboring interstitial sites

• A. If both assertion and reason are true, and reason is correct is explanation of the assertion.
• B. If both assertion and reason are true, but reason is not a correct explanation of the assertion.
• C. Assertion is true and reason is false
• D. Both Assertion and reason is false

Answer 1

Answer: (A)

On heating, $ZnO \ce{->[\Delta]} Zn ^{+2}+\frac{1}{2} O _{2}+2 e^{-}$.
This $Zn ^{+2}$ which is in excess move to interstitial sites and $e^{-} s$ to neighbouring interstitial sites
$\therefore $ it turns yellow.