Which of the following oxides is amphoteric in character?

Given oxides:

$$CaO,\ CO_2,\ SiO_2,\ SnO_2$$

Analysis:

For $$CaO$$:

$$CaO + H_2O \rightarrow Ca(OH)_2$$

It is a basic oxide.

For $$CO_2$$:

$$CO_2 + H_2O \rightarrow H_2CO_3$$

It is an acidic oxide.

For $$SiO_2$$:

$$SiO_2$$ is an acidic oxide.

For $$SnO_2$$:

It reacts with acids:

$$SnO_2 + 4HCl \rightarrow SnCl_4 + 2H_2O$$ and

also with bases:

$$SnO_2 + 2NaOH + 2H_2O$$ $$\rightarrow Na_2[Sn(OH)_6]$$

Therefore, $$SnO_2$$ exhibits both acidic and basic character.

Hence it is amphoteric.

Therefore, $${SnO_2}$$ is the amphoteric oxide.