Question

An element X reacts with oxygen and forms oxide of X which turns red litmus to blue. The element X is a :

• A. Metal
• B. Non-metal
• C. Metalloid
• D. None of these

Hint:

- Metal oxides \(\to\) Basic \(\to\) Turns Red Litmus to Blue.
- Non-metal oxides \(\to\) Acidic \(\to\) Turns Blue Litmus to Red.
This simple rule helps identify the nature of any element.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
An unknown element \(X\) reacts with oxygen to form an oxide. This oxide turns red litmus paper blue, indicating that the oxide is basic in nature. We need to identify whether \(X\) is a metal, non-metal, or metalloid.

Step 2: Key Formula or Approach:
Classify elements based on the acidic or basic nature of their oxides:
- Metal oxides are generally basic.
- Non-metal oxides are generally acidic or neutral.

Step 3: Detailed Explanation:

• When elements react with oxygen, they form oxides.

• Metals react with oxygen to form metallic oxides. These oxides are basic in nature.
- When dissolved in water, they form metal hydroxides, which release hydroxide ions (\(OH^-\)) and turn red litmus paper blue:
\[ 2Mg\text{(s)} + O_2\text{(g)} \to 2MgO\text{(s)} \] \[ MgO\text{(s)} + H_2O\text{(l)} \to Mg(OH)_2\text{(aq)} \] - Since \(Mg(OH)_2\) is basic, it turns red litmus blue.

• Non-metals react with oxygen to form non-metallic oxides, which are acidic in nature.
- When dissolved in water, they form acids that turn blue litmus paper red:
\[ SO_2\text{(g)} + H_2O\text{(l)} \to H_2SO_3\text{(aq)} \]

• Since the oxide of element \(X\) turns red litmus blue, it is confirmed to be basic.

• Therefore, element \(X\) must be a metal.


Step 4: Final Answer:
The element \(X\) is a metal.