Question

Among the following oxides of p-block elements, the number of oxides having amphoteric nature is: \[\text{Cl}_2\text{O}_7, \, \text{CO}, \, \text{PbO}_2, \, \text{N}_2\text{O}, \, \text{NO}, \, \text{Al}_2\text{O}_3, \, \text{SiO}_2, \, \text{N}_2\text{O}_5, \, \text{SnO}_2\]

Answer 1

Correct Answer: 3

The objective is to identify amphoteric oxides from a provided list of p-block element oxides and count them.

Concept Utilized:

The chemical behavior of an oxide (acidic, basic, amphoteric, or neutral) is determined by the element and its oxidation state. The classifications are as follows:

• Acidic Oxides: Typically formed by non-metals (e.g., \( \text{SO}_2, \text{CO}_2, \text{Cl}_2\text{O}_7 \)). They react with bases to produce salt and water. Acidity increases with the central non-metal's oxidation state.
• Basic Oxides: Formed by metals (e.g., \( \text{Na}_2\text{O}, \text{CaO} \)). They react with acids to produce salt and water.
• Amphoteric Oxides: Exhibit both acidic and basic properties, reacting with both acids and bases to form salt and water. Oxides of elements bordering the metal-nonmetal line in the periodic table, such as Al, Zn, Sn, and Pb, are typically amphoteric.
• Neutral Oxides: Do not react with either acids or bases. Common examples include \( \text{CO}, \text{NO}, \) and \( \text{N}_2\text{O} \).

Step-by-Step Analysis:

Each oxide in the given list will be classified:

Step 1: Oxide Classification.

1. \( \text{Cl}_2\text{O}_7 \) (Dichlorine heptoxide): Chlorine, a non-metal, is in its highest oxidation state (+7). This is a strongly acidic oxide, the anhydride of perchloric acid (\( \text{HClO}_4 \)).
2. \( \text{CO} \) (Carbon monoxide): This is a recognized neutral oxide, lacking acidic or basic properties.
3. \( \text{PbO}_2 \) (Lead(IV) oxide): Lead is a metal, and its oxides are amphoteric, reacting with both acids and bases. Example reactions: With acid: \( 2\text{PbO}_2 + 2\text{H}_2\text{SO}_4 \rightarrow 2\text{PbSO}_4 + 2\text{H}_2\text{O} + \text{O}_2 \) With base: \( \text{PbO}_2 + 2\text{NaOH} + 2\text{H}_2\text{O} \rightarrow \text{Na}_2[\text{Pb(OH)}_6] \) (Sodium plumbate) Thus, it is amphoteric.
4. \( \text{N}_2\text{O} \) (Dinitrogen monoxide): Another example of a neutral oxide.
5. \( \text{NO} \) (Nitrogen monoxide): Also a neutral oxide.
6. \( \text{Al}_2\text{O}_3 \) (Aluminum oxide): Aluminum, a metal-like element, forms a classic amphoteric oxide. It reacts with both acids and bases: With acid: \( \text{Al}_2\text{O}_3 + 6\text{HCl} \rightarrow 2\text{AlCl}_3 + 3\text{H}_2\text{O} \) With base: \( \text{Al}_2\text{O}_3 + 2\text{NaOH} + 3\text{H}_2\text{O} \rightarrow 2\text{Na}[\text{Al(OH)}_4] \) (Sodium aluminate) Thus, it is amphoteric.
7. \( \text{SiO}_2 \) (Silicon dioxide): Silicon, a metalloid, forms an acidic oxide. It reacts with strong bases to produce silicates but is largely unreactive with most acids, except hydrofluoric acid.
8. \( \text{N}_2\text{O}_5 \) (Dinitrogen pentoxide): Nitrogen, a non-metal, is in a high oxidation state (+5). This is a strongly acidic oxide, the anhydride of nitric acid (\( \text{HNO}_3 \)).
9. \( \text{SnO}_2 \) (Tin(IV) oxide): Tin, a metal, forms amphoteric oxides, reacting with strong acids and bases. With acid: \( \text{SnO}_2 + 4\text{HCl} \rightarrow \text{SnCl}_4 + 2\text{H}_2\text{O} \) With base: \( \text{SnO}_2 + 2\text{NaOH} \rightarrow \text{Na}_2\text{SnO}_3 + \text{H}_2\text{O} \) (Sodium stannate) Thus, it is amphoteric.

Step 2: Amphoteric Oxide Count.

The amphoteric oxides identified are:

• \( \text{PbO}_2 \)
• \( \text{Al}_2\text{O}_3 \)
• \( \text{SnO}_2 \)

The total count of these amphoteric oxides is three.

Final Outcome:

There are 3 oxides in the provided list that exhibit amphoteric properties.