New chat PYQ Library Doubts Rank report

Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →

D and F Block Elements question

2022 · 29 Jul · Shift 1 · Q7

Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.

PYQ Library
JEE Main
Chemistry
D and F Block Elements
2022 · 29 Jul · Shift 1 · Q7

D and F Block Elements question

2022 · 29 Jul · Shift 1 · Q7

JEE MainChemistryD and F Block ElementsMCQ+4 / −1

In neutral or faintly alkaline medium,

\mathrm{KMnO}_{4}

being a powerful oxidant can oxidize, thiosulphate almost quantitatively, to sulphate. In this reaction overall change in oxidation state of manganese will be :

A
5
B
1
C
0
D
3

View written solutionFree

Correct answer: D

Identify the oxidation state of Mn in $\mathrm{KMnO_4}$

In $\mathrm{KMnO_4}$ :

$\mathrm{K} = +1$
$4\mathrm{O} = -8$

So for Mn: $+1 + x - 8 = 0 \Rightarrow x = +7$

Thus, manganese starts at oxidation state $+7$ .

What happens to permanganate in neutral or faintly alkaline medium?

$\mathrm{KMnO_4}$ behaves differently in different media:

acidic medium: $\mathrm{MnO_4^- \to Mn^{2+}}$
neutral/faintly alkaline medium: $\mathrm{MnO_4^- \to MnO_2}$
strongly alkaline medium: $\mathrm{MnO_4^- \to MnO_4^{2-}}$

Here the medium is neutral or faintly alkaline, so Mn is reduced to $\mathrm{MnO_2}$ .

In $\mathrm{MnO_2}$ , oxidation state of Mn is: $x + 2(-2) = 0 \Rightarrow x = +4$

Calculate the overall change in oxidation state of Mn

Initial oxidation state of Mn $= +7$

Final oxidation state of Mn $= +4$

Change: $7 - 4 = 3$

So manganese undergoes a decrease of 3 units in oxidation state.

Check options

A: 5 ❌
B: 1 ❌
C: 0 ❌
D: 3 ✅

Therefore, the correct answer is D.

More from D and F Block Elements

Which of the following $3 d$ -metal ion will give the lowest enthalpy of hydration $(Δ_{hyd} H)$ when dissolved in water ?2022 · MCQ
The number of terminal oxygen atoms present in the product B obtained from the following reaction is . $F e C r_{2} O_{4}$ + $N a_{2} C O_{3}$ + $O_{2}$ $\to$ A + $F e_{2} O_{3}$ + $C O_{2}$ A + $H^{+}$ $\to$ B + $H_{2} O$ + $N a^{+}$ 2022 · Numerical
An acidified manganate solution undergoes disproportionation reaction. The spin-only magnetic moment value of the product having manganese in higher oxidation state is B.M. (Nearest integer)2022 · Numerical
The electronic configuration of Pt (atomic number 78) is :2022 · MCQ
Spin only magnetic moment of $[M n B r_{6}]^{4 -}$ is B.M. (round off to the closest integer)2022 · Numerical
For the reaction given below : $C o C l_{3}$ . x $N H_{3}$ + $A g N O_{3}$ (aq) $\to$ If two equivalents of $A g C l$ precipitate out, then the value of x will be .2022 · Numerical
Identify the element for which electronic configuration in +3 oxidation state is [Ar] $3 d_{5}$ :2021 · MCQ
In the given chemical reaction, colors of the $F e^{2 +}$ and $F e^{3 +}$ ions, are respectively : 5 $F e^{2 +}$ + MnO $_{4}^{-}$ + 8H+ $\to$ $M n^{2 +}$ + 4 $H_{2} O$ + 5 $F e^{3 +}$ 2021 · MCQ