Given below are two statements : Statement I: In the oxalic acid vs $\mathrm{KMnO}_{4}$ (in the presence of dil $\mathrm{H}_{2} \mathrm{SO}_{4}$) titration the solution needs to be heated initially to $60^{\circ} \mathrm{C}$, but no heating is required in Ferrous ammonium sulphate (FAS) vs $\mathrm{KMnO}_{4}$ titration (in the presence of dil $\mathrm{H}_{2} \mathrm{SO}_{4}$) Statement II : In oxalic acid vs $\mathrm{KMnO}_{4}$ titration, the initial formation of $\mathrm{MnSO}_{4}$ takes place at high temperature, which then acts as catalyst for further reaction. In the case of FAS vs $\mathrm{KMnO}_{4}$, heating oxidizes $\mathrm{Fe}^{2+}$ into $\mathrm{Fe}^{3-}$ by oxygen of air and error may be introduced in the experiment. In the light of the above statements, choose the correct answer from the options given below :

(B) Both Statement I and Statement II are true

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

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

(D) Both Statement I and Statement II are false

JEE Main · 2025 · 28 Jan 2025 · Shift 1 · Practical and Analytical Chemistry

Given below are two statements :

Statement I: In the oxalic acid vs

KMnO_{4}

(in the presence of dil

H_{2} SO_{4}

) titration the solution needs to be heated initially to

6 0^{\circ} C

, but no heating is required in Ferrous ammonium sulphate (FAS) vs

KMnO_{4}

titration (in the presence of dil

H_{2} SO_{4}

)
Statement II : In oxalic acid vs

KMnO_{4}

titration, the initial formation of

MnSO_{4}

takes place at high temperature, which then acts as catalyst for further reaction. In the case of FAS vs

KMnO_{4}

, heating oxidizes

Fe^{2 +}

into

Fe^{3 -}

by oxygen of air and error may be introduced in the experiment.
In the light of the above statements, choose the correct answer from the options given below :

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

Answer: (B)

Solution

Oxalic acid is oxidised by

K M n O_{4}

only sluggishly at room temperature:

2 M n O_{4}^{-} + 5 (C O O)_{2}^{2 -} + 16 H^{+} \to 10 C O_{2} + 2 M n^{2 +} + 8 H_{2} O

needs an initial temperature of about 60°C to start, after which the

M n^{2 +}

produced catalyses the rest of the reaction (autocatalysis) — so Statement I is correct. In the ferrous ammonium sulphate titration, heating is deliberately avoided because atmospheric oxygen readily oxidises

F e^{2 +}

F e^{3 +}

at raised temperature, which would introduce error — exactly what Statement II describes as the mechanistic reason. Both statements are true.

JEE Main · 2025 · 28 Jan 2025 · Shift 1 · Single correct option

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JEE Main · 2025 · 28 Jan 2025 · Shift 1 · Practical and Analytical Chemistry

Solution

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