Given below are two statements : Statement I : Mohr's salt is composed of only three types of ions-ferrous, ammonium and sulphate. Statement II : If the molar conductance at infinite dilution of ferrous, ammonium and sulphate ions are \(\mathrm{x}_{1}, \mathrm{x}_{2}\) and \(\mathrm{x}_{3} \mathrm{~S} \mathrm{~cm}^{2} \mathrm{~mol}^{-1}\), respectively then the molar conductance for Mohr's salt solution at infinite dilution would be given by \(\mathrm{x}_{1}+\mathrm{x}_{2}+2 \mathrm{x}_{3}\) In the light of the given statements, choose the correct answer from the options given below :

(C) Statement I is true but Statement II are false

(A) Both statements I and Statement II are false

(B) Statement I is false but Statement II is true

(D) Both statements I and Statement II are true

JEE Main · 2025 · 07 Apr 2025 · Shift 1 · Redox Reactions and Electrochemistry

Given below are two statements :

Statement I : Mohr's salt is composed of only three types of ions-ferrous, ammonium and sulphate.

Statement II : If the molar conductance at infinite dilution of ferrous, ammonium and sulphate ions are

x_{1}, x_{2}

and

x_{3} S cm^{2} mol^{- 1}

, respectively then the molar conductance for Mohr's salt solution at infinite dilution would be given by

x_{1} + x_{2} + 2 x_{3}

In the light of the given statements, choose the correct answer from the options given below :

(A)Both statements I and Statement II are false
(B)Statement I is false but Statement II is true
(C)Statement I is true but Statement II are false✓ Correct
(D)Both statements I and Statement II are true

Answer: (C)

Solution

Mohr's salt,

F e S O_{4} \cdot (N H_{4})_{2} S O_{4} \cdot 6 H_{2} O

, dissociates into

F e^{2 +}

, two

N H_{4}^{+}

and two

S O_{4}^{2 -}

, so it supplies only three kinds of ions---ferrous, ammonium and sulphate---and the first statement is sound. By Kohlrausch's law the limiting molar conductance adds one

F e^{2 +}

, two

N H_{4}^{+}

and two

S O_{4}^{2 -}

contributions, giving

x_{1} + 2 x_{2} + 2 x_{3}

rather than

x_{1} + x_{2} + 2 x_{3}

, so the second statement is wrong. The first statement is true while the second is false.

JEE Main · 2025 · 07 Apr 2025 · Shift 1 · Single correct option

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JEE Main · 2025 · 07 Apr 2025 · Shift 1 · Redox Reactions and Electrochemistry

Solution

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