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Science (086) — CBSE Class 10 board question

Q1. [1] § 2.1 UNDERSTANDING THE CHEMICAL PROPERTIES OF ACIDS AND BASES § 2.4 MORE ABOUT SALTS
You have three aqueous solutions A, B and C as given below : A - Potassium nitrate B - Ammonium chloride C - Sodium carbonate The ascending order of the pH of these solutions is :
  1. (A) A < B < C
  2. (B) B < C < A
  3. (C) C < A < B
  4. (D) B < A < C
Previously asked in CBSE board exam
2025 31/6/1 Q2
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Model Answer

(D) B < A < C

Ammonium chloride (strong acid + weak base → acidic, pH < 7), potassium nitrate (strong acid + strong base → neutral, pH = 7), sodium carbonate (strong base + weak acid → basic, pH > 7).

Explanation

From section 2.4.2: salts of strong acid + weak base are acidic (pH < 7); strong acid + strong base are neutral (pH = 7); strong base + weak acid are basic (pH > 7). NH₄Cl = HCl + NH₄OH (weak base) → acidic; KNO₃ = HNO₃ + KOH (both strong) → neutral; Na₂CO₃ = NaOH + H₂CO₃ (weak acid) → basic. So ascending pH order: B < A < C.

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