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99 Percentile Qs Bank for JEE MainChemistryRedox Reactions

18.3 g of a pure monobasic organic acid containing two 'O' atoms per molecule is burnt completely in excess of oxygen and CO 2 evolved is absorbed completely in one litre of an aqueous solution of NaOH. A 10 mL portion of this solution required 14.5 mL of a normal HCl solution to reach the phenolphthalein end point. An another 10 mL portion of the same solution required 25 mL of the same HCl solution to reach the met

Options

  1. A2.5 N
  2. B3.5 N
  3. C1.5 N
  4. D4.5

Correct answer

A. 2.5 N

Step-by-step solution

Reaction of CO 2 & NaOH 2 N a O H + C O 2 ⟶ N a 2 C O 3 + H 2 O Let 10 mL final solution has x mM Na 2 CO 3 and y mM of NaOH y + x = 14.5 (Phenolphthalein) y + 2x = 25.0 ( Methyl orange) Total mM of Na 2 CO 3 Produced = 1 0 . 5 × 1 0 0 = 1 0 5 0 mM = mM of CO 2 x = 10.5 y = 4 2 N a O H 2 × 10.5 + CO 2 10.5 → N a 2 C O 3 + H 2 O ∴ Initial N a O H in 10 m l = 21 + 4 = 25 m m o l e Normality = 25 10 = 2.5 N

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