Q.(a) Classify following oxides as neutral, acidic, basic or amphoteric:
CO, B2O3, SiO2, CO2, Al2O3, PbO2, Tl2O3

CO is neutral (does not react with acids or bases under normal conditions). B$_2$O$_3$, SiO$_2$ and CO$_2$ react only with bases, forming borates/silicates/carbonates. Al$_2$O$_3$ and PbO$_2$ react with both acids and bases (amphoteric). Tl$_2$O$_3$ reacts only with acids (basic oxide), consistent with thallium's Group 1-like +1/ +3 …

(a) Classification

(b) Supporting equations

1. CO (neutral): Does not react appreciably with either dilute acids or bases — it has no oxide-like acid/base character (unlike CO$_2$), consistent with its neutral classification.

2. B$_2$O$_3$ (acidic): Reacts with a base to form a borate, and with water to give boric acid:

3. SiO$_2$ (acidic): Reacts with hot concentrated alkali to form a silicate:

4. CO$_2$ (acidic): Reacts with base to form a carbonate (and dissolves in water to give carbonic acid):

5. Al$_2$O$_3$ (amphoteric): Reacts with both acid and base:

$\text{Al}_2\text{O}_3 + 2\text{NaOH} \rightarrow 2\text{NaAlO}_2 + \text{H}_2\text{O}$ …

Classify each oxide by recalling the general trend that oxides become progressively more basic down a group and more acidic across a period towards the right, with borderline elements (Al, Pb, Tl at lower oxidation states) showing amphoteric or basic behaviour. Then write the charac …

• Classifying Al$_2$O$_3$ or PbO$_2$ as purely basic or purely acidic instead of correctly identifying them as amphoteric (reacting with both acid and base). …