Advertisements
Advertisements
Question
Why are Mn2+ compounds more stable than Fe2+ towards oxidation to their +3 state?
Advertisements
Solution
- The electronic configuration of Mn2+ is [Ar] 3d5 while that of Fe2+ is [Ar] 3d6.
- Since Mn2+ has a half-filled orbit (3d5), it is not easily oxidised to Mn3+ because of its very high third ionization enthalpy.
- In contrast, Fe2+ compounds are easily oxidised to Fe3+ due to a lower third ionization enthalpy, which results in the more stable half-filled 3d5 configuration.
- This is the reason why Mn2+ compounds are more stable than Fe2+ towards oxidation to their +3 state.
APPEARS IN
RELATED QUESTIONS
Which metal in the first transition series (3d series) exhibits + 1 oxidation state most frequently and why?
How would you account for the irregular variation of ionization enthalpies (first and second) in the first series of the transition elements?
The paramagnetic character in the 3d-transition series elements increases up to Mn and then decreases.
Account for the following :
Ti4+ is colourless whereas V4+ is coloured in an aqueous solutions.
Why is \[\ce{HCl}\] not used to make the medium acidic in oxidation reactions of \[\ce{KMnO4}\] in acidic medium?
Which of the following will not act as oxidising agents?
(i) \[\ce{CrO3}\]
(ii) \[\ce{MoO3}\]
(iii) \[\ce{WO3}\]
(iv) \[\ce{CrO^{2-}4}\]
Although fluorine is more electronegative than oxygen, but the ability of oxygen to stabilise higher oxidation states exceeds that of fluorine. Why?
Explain why does colour of KMnO4 disappear when oxalic acid is added to its solution in acidic medium.
The second and third rows of transition elements resemble each other much more than they resemble the first row. Explain why?
EΘ of Cu is + 0.34V while that of Zn is – 0.76V. Explain.
The halides of transition elements become more covalent with increasing oxidation state of the metal. Why?
Reactivity of transition elements decreases almost regularly from Sc to Cu. Explain.
Match the properties given in Column I with the metals given in Column II.
| Column I (Property) | Column II (Metal) | |
| (i) | An element which can show +8 oxidation state | (a) \[\ce{Mn}\] |
| (ii) | 3d block element that can show | (b) \[\ce{Cr}\] |
| upto +7 oxidation state | (c) \[\ce{Os}\] | |
| (iii) | 3d block element with highest melting point | (d) \[\ce{Fe}\] |
Mention the type of compounds formed when small atoms like H, C and N get trapped inside the crystal lattice of transition metals. Also give physical and chemical characteristics of these compounds.
On the basis of the figure given below, answer the following questions:
- Why Manganese has lower melting point than Chromium?
- Why do transition metals of 3d series have lower melting points as compared to 4d series?
- In the third transition series, identify and name the metal with the highest melting point.
Photographic film and plates have - au essential ingredient of
Assertion (A): Transition metals have high enthalpy of atomisation.
Reason (R): Greater number of unpaired electrons in transition metals results in weak metallic bonding.
Complete the following reaction and justify that it is a disproportionation reaction:
\[\ce{3MnO^{2-}4 + 4H^+ -> \underline{}\underline{}\underline{}\underline{} + \underline{}\underline{}\underline{}\underline{} + 2H2O}\]
Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with H2S.
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.
