A metal M forms an oxide having the formula M2O3. It dissolves both in dilute sulphuric acid and dilute hydroxide solution.
The correct answer and explanation is:
The metal M forms an oxide with the formula M₂O₃ and dissolves in both dilute sulfuric acid and dilute hydroxide solution.
Correct Answer:
The metal M is amphoteric.
Explanation:
- Oxide Formula M₂O₃
The formula M₂O₃ indicates that the metal M forms a metal oxide where the metal is in the +3 oxidation state. Common examples include aluminum (Al₂O₃), chromium (Cr₂O₃), and iron(III) oxide (Fe₂O₃). - Dissolving in Dilute Sulfuric Acid (H₂SO₄)
When M₂O₃ dissolves in dilute sulfuric acid, it reacts as a base to form a salt and water:
M2O3+3H2SO4→2MSO4+3H2OM_2O_3 + 3H_2SO_4 \rightarrow 2MSO_4 + 3H_2O
This behavior is typical of basic or amphoteric oxides, which can react with acids.
- Dissolving in Dilute Hydroxide (NaOH or KOH)
If the oxide also dissolves in dilute hydroxide solution, it means it can react with bases, forming complex ions or salts. This property is characteristic of amphoteric oxides, which react with both acids and bases.
For example, aluminum oxide reacts with sodium hydroxide as: Al2O3+2NaOH+3H2O→2Na[Al(OH)4]Al_2O_3 + 2NaOH + 3H_2O \rightarrow 2Na[Al(OH)_4]
Here, the oxide dissolves to form a soluble aluminate complex.
- Amphoteric Nature
- Basic oxides only react with acids.
- Acidic oxides only react with bases.
- Amphoteric oxides react with both acids and bases.
Since M₂O₃ dissolves in both dilute acid and base, M₂O₃ is an amphoteric oxide.
Summary
The oxide M₂O₃ is formed by a metal in +3 oxidation state. Its ability to dissolve in both dilute sulfuric acid and dilute hydroxide solution confirms that it behaves as an amphoteric oxide. Amphoteric oxides have a dual chemical nature, reacting with acids to form salts and water, and with bases to form complex ions or salts, depending on the solution. Examples include aluminum oxide (Al₂O₃), chromium(III) oxide (Cr₂O₃), and zinc oxide (ZnO, though ZnO formula differs, it is amphoteric). This behavior is key in identifying metals with amphoteric properties, often located in the middle of the periodic table, such as aluminum and chromium.