Download App

The d & f Block Elements — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryThe d & f Block Elements1 Mark
MCQ
When $\ce{KMnO_4}$ solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because
  • A
    $\text{CO}_2$is formed as the product.
  • B
    Reaction is exothermic.
  • C
    $\text{MnO}_4^-$ catalyses the reaction.
  • ✓
    $\text{Mn}^{2+}$acts as autocatalyst.
✓

Answer

Correct option: D.
$\text{Mn}^{2+}$acts as autocatalyst.
When $\ce{KMnO_4}$ solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because $Mn^{2+}$ acts as an autocatalyst.
Reduction half $[\text{MnO}^-_4+8\text{H}^++5\text{e}^-\rightarrow\text{Mn}^{2+}+4\text{H}_2\text{O]}\times2$
Oxidation half $[\text{C}_2\text{O}_4^{2-}\rightarrow2\text{CO}_2+2\text{e}^-]\times5$
Overall equation $2\text{MnO}_4^-+16\text{H}^++5\text{C}_2\text{O}_4^{2-}\rightarrow2\text{Mn}^{2+}+10\text{CO}_2+8\text{H}_2\text{O}$
End point of this reaction Colourless to light pink

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "M.C.Q (1 Marks)" from The d & f Block Elements→The d & f Block Elements — all question types→Chemistry STD 12 Science question papers→Gujarat Board STD 12 Science question papers→Gujarat Board question paper generator→

Similar questions

In mildly alkaline medium, thiosulphate ion is oxidized by $MnO _{4}^{-}$ to $"A".$ The oxidation state of sulphur in $"A"$ is ..... .
→
$N_2 + 3H_2 \to 2NH_3$ Concentration of $NH_3$ changes from $0.01\, M$ to $0.04\, M$ in $20\, seconds$ then rate of reaction will be
→
Grapes placed in three beakers $X, Y$ and $Z$ containing different types of solution are shown in figures. If beaker $X$ contains isotonic solution with grape solution then $Y$ and $Z$ will contain
→
The ionization isomer of $\left[\mathrm{Cr}\left(\mathrm{H}_2 \mathrm{O}\right)_4 \mathrm{Cl}\left(\mathrm{NO}_2\right)\right] \mathrm{Cl}$ is
→
Milk of magnesia is used as:
→
The number of hydroxyl group in pyrophosphoric acid is
→
Which of the followings is most reactive toward hydrolysis
→
Elements in which $4f$ orbitals are progressively filled are called as
→
The electronic configuration $1{s^2},2{s^2}{p^6},3{s^2}{p^6}{d^6}$ corresponds to
→
Which one of the following is the strongest base in aque­ous solution ?
→