Question

Which of the following dioxide is amphoteric in nature?

• A. CaO
• B. SiO₂
• C. CO₂
• D. SnO₂

Answer 1

The correct option is D

SnO₂

Explanation for correct option:

(D) ${\mathrm{SnO}}_2$

• ${\mathrm{SnO}}_2$ reacts with acid as well as the base to form corresponding salts.
• Thus, it is amphoteric dioxide.
• The chemical reaction is as follows:-
• ${\mathrm{SnO}}_2\left(\mathrm{s}\right)+4\mathrm{HCl}\left(\text{g}\right)\to {\mathrm{SnCl}}_4\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\text{l}\right)$
• ${\mathrm{SnO}}_2\left(\mathrm{s}\right)+2\mathrm{NaOH}\left(\mathrm{s}\right)\to {\mathrm{Na}}_2{\mathrm{SnO}}_3\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Explanation for incorrect options:

(A) $\mathrm{CaO}$

• Calcium oxide is a basic oxide.
• As $\mathrm{CaO}$ dissolves in water, it gives calcium hydroxide $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$.
• $\mathrm{CaO}+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to \mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)$
• Thus, it is not an amphoteric oxide.

(B) ${\mathrm{SiO}}_2$

• Silicon dioxide reacts with strong bases. it is acidic in nature.
• ${\mathrm{SiO}}_2\left(\mathrm{s}\right)+2\mathrm{NaOH}\left(\mathrm{s}\right)\to {\mathrm{Na}}_2{\mathrm{SiO}}_3\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$
• Thus, it is not an amphoteric oxide.

(C) ${\mathrm{CO}}_2$

• Carbon dioxide is acidic in nature.
• Carbon dioxide on treatment with water results in carbonic acid ${\mathrm{H}}_2{\mathrm{CO}}_3$ formation. Thus it accepts 2 pairs of electrons.
• ${\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to {\mathrm{H}}_2{\mathrm{CO}}_3\left(\mathrm{aq}\right)$
• It behaves as an acidic oxide.
• Therefore, it is not an amphoteric oxide.

Hence, the correct option is (D) ${\mathrm{SnO}}_2$