JEE Main · 2025 · Shift-IIhardRDX-081

0.1 M solution of KI reacts with excess of H2SO4 and KIO3 solution. According to equation 5I- + IO3- + 6H+ - 3I2 + 3H2O…

Redox Reactions · Class 11 · JEE Main Previous Year Question

Question

0.1 M solution of KI reacts with excess of \ceH2SO4\ce{H2SO4} and \ceKIO3\ce{KIO3} solution. According to equation

\ce5I+IO3+6H+>3I2+3H2O\ce{5I^- + IO3^- + 6H^+ -> 3I2 + 3H2O}

Identify the correct statements:

(A) 200 mL of KI solution reacts with 0.004 mol of \ceKIO3\ce{KIO3}

(B) 200 mL of KI solution reacts with 0.008 mol of \ceH2SO4\ce{H2SO4}

(C) 0.5 L of KI solution produced 0.005 mol of \ceI2\ce{I2}

(D) Equivalent weight of \ceKIO3\ce{KIO3} is equal to (Molecular weight5)\left(\dfrac{\text{Molecular weight}}{5}\right)

Choose the correct answer from the options given below:

Options
  1. a

    (A) and (D) only

  2. b

    (B) and (C) only

  3. c

    (A) and (B) only

  4. d

    (C) and (D) only

Correct Answera

(A) and (D) only

Detailed Solution

Given: 0.1 M KI solution; balanced equation: \ce5I+IO3+6H+>3I2+3H2O\ce{5I^- + IO3^- + 6H^+ -> 3I2 + 3H2O}

Step 1 — Moles of KI in 200 mL

n(\ceKI)=0.1×0.200=0.02n(\ce{KI}) = 0.1 \times 0.200 = 0.02 mol = 0.02 mol \ceI\ce{I^-}

Check Statement A: Moles of \ceKIO3\ce{KIO3} required

From stoichiometry: 5 mol \ceI5\text{ mol }\ce{I^-} reacts with 1 mol \ceIO31\text{ mol }\ce{IO3^-}

n(\ceIO3)=0.025=0.004n(\ce{IO3^-}) = \frac{0.02}{5} = 0.004 mol ✓

Statement A is CORRECT

Check Statement B: Moles of \ceH2SO4\ce{H2SO4} required

6 mol \ceH+6\text{ mol }\ce{H^+} per mol \ceIO3\ce{IO3^-}; \ceH2SO4\ce{H2SO4} gives 2 \ceH+\ce{H^+}

n(\ceH+)=6×0.004=0.024n(\ce{H^+}) = 6 \times 0.004 = 0.024 mol

n(\ceH2SO4)=0.0242=0.012n(\ce{H2SO4}) = \frac{0.024}{2} = 0.012 mol ≠ 0.008 mol ✗

Statement B is INCORRECT

Check Statement C: \ceI2\ce{I2} from 0.5 L of 0.1 M KI

n(\ceI)=0.1×0.5=0.05n(\ce{I^-}) = 0.1 \times 0.5 = 0.05 mol

n(\ceI2)=35×0.05=0.03n(\ce{I2}) = \frac{3}{5} \times 0.05 = 0.03 mol ≠ 0.005 mol ✗

Statement C is INCORRECT

Check Statement D: Equivalent weight of \ceKIO3\ce{KIO3}

In this reaction, \ceI\ce{I} in \ceIO3\ce{IO3^-} goes from +5 to 0 (in \ceI2\ce{I2}): change = 5 electrons per I atom.

Equivalent weight =M(\ceKIO3)5=2145= \frac{M(\ce{KIO3})}{5} = \frac{214}{5}

Statement D is CORRECT

Answer: (A) and (D) only → Option (a)

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