Question

A magnesium ribbon is burnt in air to form a substance X. When X is dissolved in water, a new substance Y is formed. When Y is tested with red litmus paper, the colour of red litmus paper turns to blue. Then which of the following statements is not true?

• A. Substance X is basic in nature.
• B. Substance X is magnesium oxide.
• C. Substance Y is magnesium hydroxide.
• D. Substance Y is magnesium oxide.

Answer 1

The correct option is D Substance Y is magnesium oxide.

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Magnesium ribbon, on burning, reacts with oxygen to form magnesium oxide.

$\text{Magnesium + Oxygen}\to \text{Magnesium oxide}$

Therefore, substance X is magnesium oxide.

When magnesium oxide is dissolved in water, magnesium hydroxide is formed.

$\text{Magnesium oxide + Water}\to \text{Magnesium hydroxide}$

Therefore, substance Y is magnesium hydroxide.

A red litmus turns blue when it is dipped in a solution which is basic in nature. Since the colour of red litmus paper turns to blue when dipped in substance Y (magnesium hydroxide), it shows that magnesium hydroxide is basic in nature. Thus magnesium oxide (Substance X) will also be basic in nature.