Q1. [1] § 2.1 UNDERSTANDING THE CHEMICAL PROPERTIES OF ACIDS AND BASES
An aqueous solution of a salt turns blue litmus to red. The salt could be the one obtained by the reaction of :
- A HNO₃ and NaOH
- B H₂SO₄ and KOH
- C CH₃COOH and NaOH
- D HCl and NH₄OH
Previously asked in CBSE board exam
2024 31/4/1 Q2
Generated by claude-sonnet-4-6 · 2026-06-15 06:44 · grounding rag
Model Answer
Answer: D
HCl (strong acid) + NH₄OH (weak base) → NH₄Cl (acidic salt, pH < 7), which turns blue litmus red.
Source: Acids, Bases and Salts, Section 2.4.2
Explanation
- A salt turns blue litmus red only if it is acidic (pH < 7).
- Salts of strong acid + weak base are acidic.
- Option D: HCl (strong acid) + NH₄OH (weak base) → NH₄Cl — acidic salt ✓
- Options A & B: strong acid + strong base → neutral salt (no litmus change).
- Option C: CH₃COOH (weak acid) + NaOH (strong base) → basic salt (turns red litmus blue, not the other way).
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