(a) Neutral oxides: \(\mathrm{CO}\); Acidic oxides: \(\mathrm{B}_2 \mathrm{O}_3, \mathrm{SiO}_2, \mathrm{CO}_2\) Amphoteric oxides : \(\mathrm{Al}_2 \mathrm{O}_3, \mathrm{PbO}_2\) Basic oxide : \(\mathrm{Tl}_2 \mathrm{O}_3\)
(b) (i) Being acidic, \(\mathrm{B}_2 \mathrm{O}_3, \mathrm{SiO}_2\) and \(\mathrm{CO}_2\) react with alkalis to form salts.
\(\mathrm{B}_2 \mathrm{O}_3+2 \mathrm{NaOH} \longrightarrow 2 \mathrm{NaBO}_2+\mathrm{H}_2 \mathrm{O}\)
\(\mathrm{SiO}_2+2 \mathrm{NaOH} \longrightarrow \mathrm{Na}_2 \mathrm{SiO}_3+\mathrm{H}_2 \mathrm{O}\)
\(\mathrm{CO}_2+2 \mathrm{NaOH} \longrightarrow \mathrm{Na}_2 \mathrm{CO}_3+\mathrm{H}_2 \mathrm{O}\)
(ii) Being basic, \(\mathrm{Tl}_2 \mathrm{O}_3\) dissolves in acids
\(\mathrm{Tl}_2 \mathrm{O}_3+6 \mathrm{HCl} \longrightarrow 2 \mathrm{TlCl}_3+3 \mathrm{H}_2 \mathrm{O}\)
(iii) Being amphoteric, \(\mathrm{Al}_2 \mathrm{O}_3\) and \(\mathrm{PbO}_2\) react with both acids and bases.
\(\mathrm{Al}_2 \mathrm{O}_3+2 \mathrm{NaOH} \longrightarrow 2 \mathrm{NaAlO}_2+\mathrm{H}_2 \mathrm{O}\)
\(\mathrm{Al}_2 \mathrm{O}_3+3 \mathrm{H}_2 \mathrm{SO}_4 \longrightarrow \mathrm{Al}_2\left(\mathrm{SO}_4\right)_3+3 \mathrm{H}_2 \mathrm{O}\)
\(\mathrm{PbO}_2+2 \mathrm{NaOH} \longrightarrow \mathrm{Na}_2 \mathrm{PbO}_3+\mathrm{H}_2 \mathrm{O}\)
\(2 \mathrm{PbO}_2+2 \mathrm{H}_2 \mathrm{SO}_4 \longrightarrow 2 \mathrm{PbSO}_4+2 \mathrm{H}_2 \mathrm{O}+\mathrm{O}_2\)