Advertisements
Advertisements
Question
When \[\ce{KMnO4}\] solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because ______.
Options
\[\ce{CO2}\] is formed as the product.
Reaction is exothermic.
\[\ce{MnO^{-}4}\] catalyses the reaction.
\[\ce{MnO^{2+}}\] acts as autocatalyst.
Advertisements
Solution
When \[\ce{KMnO4}\] solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because \[\ce{MnO^{2+}}\] acts as autocatalyst.
Explanation:
When \[\ce{KMnO4}\] solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because \[\ce{Mn^{2+}}\] acts as an autocatalyst.
Reduction half \[\ce{Mno^{-}4 + 8H^+ + 5e^- -> Mn^{2+} + 4H2O] × 2}\]
Oxidation half \[\ce{C2O^{2-}4 -> 2CO2 + 2e] × 5}\]
Overall equation \[\ce{2Mno^{-}4 + 16H^+ + 5C2O^{2-}4 -> 2Min^{2+} + 10CO2 + 8H2O}\]
End point of this reaction Colourless to light pink.
APPEARS IN
RELATED QUESTIONS
Out of Mn3+ and Cr3+, which is more paramagnetic and why ?
(Atomic nos. : Mn = 25, Cr = 24)
Explain why Cu+ ion is not stable in aqueous solutions?
Why are Mn2+ compounds more stable than Fe2+ towards oxidation to their +3 state?
What are the characteristics of the transition elements and why are they called transition elements?
Use Hund’s rule to derive the electronic configuration of Ce3+ ion and calculate its magnetic moment on the basis of ‘spin-only’ formula.
Explain why transition elements form alloys.
Metallic radii of some transition elements are given below. Which of these elements will have highest density?
| Element | \[\ce{Fe}\] | \[\ce{Co}\] | \[\ce{Ni}\] | \[\ce{Cu}\] |
| Metallic radii/pm | 126 | 125 | 125 | 128 |
Generally transition elements form coloured salts due to the presence of unpaired electrons. Which of the following compounds will be coloured in solid-state?
Transition elements show magnetic moment due to spin and orbital motion of electrons. Which of the following metallic ions have almost same spin only magnetic moment?
(i) \[\ce{Co^{2+}}\]
(ii) \[\ce{Cr^{2+}}\]
(iii) \[\ce{Mn^{2+}}\]
(iv) \[\ce{Cr^{3+}}\]
Explain why does colour of KMnO4 disappear when oxalic acid is added to its solution in acidic medium.
Answer the following question:
Which element of the first transition series has lowest enthalpy of atomisation?
Why are fluorides of transition metals more stable in their higher oxidation state as compared to the lower oxidation state?
It has been observed that first ionization energy of 5 d series of transition elements are higher than that of 3d and 4d series, explain why?
Among the following pairs of ions, the lower oxidation state in aqueous solution is more stable than the other in:-
Give reasons for the following statement:
Zn, Cd, and Hg are soft metals.
The electrode potential of M2+/M of 3d-series elements shows the positive value for ______.
Which of the following characteristics of transition metals is associated with their catalytic activity?
For M2+/M and M3+/M2+systems, the EΘ values for some metals are as follows:
| Cr2+/Cr | −0.9 V |
| Mn2+/Mn | −1.2 V |
| Fe2+/Fe | −0.4 V |
| Cr3/Cr2+ | −0.4 V |
| Mn3+/Mn2+ | +1.5 V |
| Fe3+/Fe2+ | +0.8 V |
Use this data to comment upon:
The ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.
Compare the general characteristics of the first series of the transition metals with those of the second and third series metals in the respective vertical columns. Give special emphasis on the following point:
Atomic sizes
