Question

Generally, metallic oxides are basic and non-metallic oxides are acidic in nature. The solution of which of the following oxides in water will change the color of blue litmus to red?

• A. Sulfur dioxide
• B. Magnesium oxide
• C. Iron oxide
• D. Copper oxide

Answer 1

The correct option is A

Sulfur dioxide

The correct option is Option A

The explanation for the correct option:

1. Metal oxides are basic in nature.
2. Because they react with weak acids to produce salt and water, metallic oxides are basic in nature.
3. Additionally, they react with water to create metal hydroxides, which are naturally alkaline because they release ${\mathrm{OH}}^{-}$ ions into the solution.
4. Non-metal oxides are acidic in nature.
5. Water and non-metal oxides react to create acidic solutions that release ${\mathrm{H}}^{+}$ ions into the solution.
6. Sulfur oxide reacts with water to give sulfuric acid. $\underset{\mathrm{Sulfur}\mathrm{dioxide}}{{\mathrm{SO}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\to \underset{\mathrm{sulfuric}\mathrm{acid}}{{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{l}\right)}+2\mathrm{H}$
7. Being a very strong acid, sulfuric acid totally ionizes in aqueous solutions to produce hydrogen ions (${\mathrm{H}}_3{\mathrm{O}}^{+}$) and sulfate ions (${{\mathrm{HSO}}_4}^{-}$).

The explanation for the incorrect options:

Option (B): Magnesium oxide

1. Due to the presence of oxide ions, magnesium oxide is a basic oxide. Magnesium hydroxide, a base is produced when it interacts with water.
2. It will convert red litmus to blue.
3. Hence, it is an incorrect option.

Option (C): Iron oxide

1. The iron oxides are amphoteric chemical species, meaning they possess both basic and acidic properties.
2. There will be no change in litmus paper due to its amphoteric nature.
3. Hence, it is an incorrect option.

Option (D): Copper oxide

1. In general, metal oxides have a basic character, whereas non-metal oxides have an acidic nature.
2. Due to the fact that copper oxide is a metallic oxide, it has a basic nature so it will convert red litmus to blue.
3. Hence, it is an incorrect option.

Final answer: Sulfur dioxide changes blue litmus to red.