Long Answer TypeFor M2+/M and M3+/M2+ systems the E° values for some metals are as follows:
Cr2+/Cr – 0.9 V Cr3+/Cr2+ – 0.4 V
Mn2+/Mn – 1.2 V Mn3+/Mn2+ + 1.5 V
Fe2+/Fe – 0.4 V Fe3+/Fe2+ + 0.8 V
Use this data to comment upon
(a) The stability of Fe3+ in acid solution as compared to that of Cr3+ or Mn3+ and
(b) In case with which iron can be oxidised as compared to the similar process for either chromium or manganese metal
Predict which of the following will be coloured in aqueous solution? Ti3+, V3+, Cu+, Sc3+, Mn2+, Fe3+ and Co2+. Give reason for each.
Short Answer TypeCompare the chemistry of actinides with that of the lanthanoids with special reference to:
(i) electronic configuration, (ii) atomic and ionic sizes, (iii) oxidation state (iv) chemical reactivity.
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Characteristics |
Lanthanoids |
Actinides |
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(a) Electronic configuration |
It may be represented by [Xe]4fx 5dy 6s2, where x varies from 0 to 14 and y = 0 or 1. |
It may be represented by [Rn]5fx 6dy 7s2,where x varies from 0 to 14 and y = 0 or 1. |
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(b) Oxidation state
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Show +3 oxidation state only except in few cases where it is +2 or +4. They never show more than +4 state. |
Show higher oxidation states such as +4, +5, +6, +7 also in addition to +3.
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(c) atomic and ionic sizes
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The ionic radii of M3+ ions in lanthanoids series show a regular decrease in size of ions with increase in atomic number. This decrease is known as lanthanoid contraction. |
There is a greater and gradual decrease in the size of atoms or M3+ ions across the series. This greater decrease is known as actinoid contraction.
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(d) Chemical reactivity |
These are less reactive metals and form oxides, sulphides, nitrides, hydroxides and halides etc. These also form H2 with acids. They show a lesser tendency for complex formation |
These are highly reactive metals especially when are in finely divided state. They form a mixture of oxide and hydride by action of boiling water. They combine with non-metals even at moderate temperature. They show a greater tendency for complex formation. |
Long Answer TypeHow would you account for the following:
(a) Of the d4 species, Cr2+ is strongly reducing while manganese(III) is strongly oxidising.
(b) Cobalt(II) is stable in aqueous solution but in the presence of complexing reagents it is easily oxidized.
(c) The d1 configuration is very unstable in ions.
Short Answer Type
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