Question

Which one is acidic?

• A. \( \text{MnO} \)
• B. \( \text{Mn}_2\text{O}_3 \)
• C. \( \text{MnO}_2 \)
• D. \( \text{Mn}_2\text{O}_7 \)

Hint:

Oxides of metals with high oxidation states (such as Mn in +7) are usually acidic, while oxides of metals with lower oxidation states (like +2) are typically basic.

Answer 1

The Correct Option is D

In chemistry, the nature of an oxide—whether acidic, basic, or amphoteric—depends on the oxidation state of the metal and its position in the periodic table. For transition metals, higher oxidation states generally form oxides that are more acidic.

Let's analyze the given options:

• \( \text{MnO} \): Manganese is in the +2 oxidation state. This oxide exhibits basic properties.
• \( \text{Mn}_2\text{O}_3 \): Manganese is in the +3 oxidation state. It is weakly acidic or amphoteric.
• \( \text{MnO}_2 \): Manganese is in the +4 oxidation state. It is amphoteric, showing both acidic and basic properties.
• \( \text{Mn}_2\text{O}_7 \): Manganese is in the +7 oxidation state. This is highly oxidized, making it strongly acidic.

Therefore, the compound \( \text{Mn}_2\text{O}_7 \) is acidic.