Q1. [2] § 2.1 UNDERSTANDING THE CHEMICAL PROPERTIES OF ACIDS AND BASES
Two solutions M and N give Red and Blue colour respectively with a universal indicator.
(i) In which solution will the hydrogen ion concentration be more ? Justify your answer.
(ii) If both M and N solutions are mixed and the resultant mixture is tested with a universal indicator, it turns green. What is the nature of the salt formed ? Justify your answer.
Previously asked in CBSE board exam
2023 31/5/1 Q21 (b)
Generated by claude-sonnet-4-6 · 2026-06-15 06:45 · grounding rag
Model Answer
(i) Solution M gives red colour with universal indicator, indicating it is acidic (pH < 7). Therefore, solution M has more hydrogen ion (H⁺) concentration, since higher H⁺ concentration corresponds to lower pH and acidic nature.
(ii) When M and N are mixed and the result turns green, the pH is 7 (neutral). The salt formed is a neutral salt, formed by the reaction of a strong acid and a strong base. Salts of strong acid and strong base have pH = 7.
Source: Chapter 2, Sections 2.3 and 2.4.2
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Explanation
- Universal indicator: red = acidic (low pH, high H⁺); blue = basic (high pH, low OH⁻).
- Green on universal indicator = pH 7 = neutral. CBSE expects you to link green colour → neutral salt → strong acid + strong base. Both justifications are essential for full marks.
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