Question

4. A salt X when dissolved in distilled water gives a clear solution which turns red litmus blue. Explain this phenomenon.

Answer 1

Answer: Salt X is the basic salt.

Explanation:

A basic salt is the salt which when dissolved in water will give us a basic solution. These salts will turn red litmus blue.

An acidic salt is the salt which when dissolved in water will give us acidic solution and will turn blue litmus red.

In the question, it is given that salt 'X' is dissolved in water and it also turns red litmus blue. Thus, the unknown salt 'X' is considered as a basic salt.

Hence, salt X is the basic salt.

Answer 2

Explanation:

• Litmus paper test is used to identify the nature of solutions.
• If solution turns blue to red solutions have acidic nature.
• If solution turns red to blue solutions have basic nature.

• A salt X which is “dissolved in distilled water” gives a clear solution which turns “red litmus blue” means it is a basic solution.

• Sodium carbonate is dissolved in water to give sodium hydroxide and carbonic acid.

The chemical reaction is as follows:

$N a_{2} C O_{3}(s)+2 H_{2} O(l) \stackrel{\text { Hydrolysis }}{\longrightarrow} 2 N a O H(a q)+H_{2} C O_{3}(a q)$

• In the above reaction, the products are sodium hydroxide and carbonic acid. These are strong base and carbonic acid respectively. Hence, sodium carbonate solution turns red colour to blue colour.