Find the amphoteric oxide

The correct option is SnO₂.

An amphoteric oxide is a chemical compound (specifically an oxide of a metal or metalloid) that can act as either an acid or a base to produce water and a salt. This means it is capable of reacting with both acids and strong bases.

Let us analyze the nature of the oxides given in the options to understand why SnO₂ (tin dioxide) is amphoteric:

1. CaO₂ (Calcium peroxide): Calcium is an alkaline earth metal (Group 2). Its oxides and peroxides are basic in nature because they react with acids to form salts and water (or hydrogen peroxide), but they do not react with bases.
2. CO��� (Carbon dioxide): Carbon is a non-metal. Non-metal oxides typically form acidic solutions when dissolved in water. CO₂ reacts with water to form carbonic acid (H₂CO₃) and reacts readily with bases (like NaOH) to form carbonates, but it does not react with acids. Thus, it is an acidic oxide.
3. SiO₂ (Silicon dioxide): Silicon is a metalloid/non-metal. SiO₂ is weakly acidic; it reacts with strong hot bases (like NaOH) to form silicates, but it does not react with ordinary acids (except hydrofluoric acid due to specific silicon-fluorine affinity). Therefore, it is classified as an acidic oxide.
4. SnO₂ (Tin dioxide): Tin (Sn) is a metal located in Group 14 of the periodic table. Oxides of elements near the metal-nonmetal boundary often display amphoteric behavior. Tin(IV) oxide (SnO₂) reacts with both strong acids and strong bases, demonstrating its amphoteric nature.

This dual behavior can be illustrated by the following chemical reactions:

• Reaction with a strong acid (acting as a base):
When tin dioxide reacts with concentrated hydrochloric acid, it forms tin(IV) chloride and water:
$${\mathrm{SnO}}_2+4\mathrm{HCl}\to {\mathrm{SnCl}}_4+2H_{2}O$$

• Reaction with a strong base (acting as an acid):
When tin dioxide is fused with sodium hydroxide, it reacts to form sodium stannate and water:
$${\mathrm{SnO}}_2+2\mathrm{NaOH}\to {\mathrm{Na}}_2{\mathrm{SnO}}_3+H_{2}O$$

Since SnO₂ is the only oxide among the choices that reacts with both acids and bases to undergo neutralization, it is the amphoteric oxide.