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Chemistry
The D-and F-Block Elements
NCERT Solutions
NCERT Solutions
The D-and F-Block Elements
25 Solutions
Q1
Exercises
Write down the electronic configuration of:
(i)
Cr
3
+
\text{Cr}^{3+}
Cr
3
+
(ii)
Pm
3
+
\text{Pm}^{3+}
Pm
3
+
(iii)
Cu
+
\text{Cu}^{+}
Cu
+
(iv)
Ce
4
+
\text{Ce}^{4+}
Ce
4
+
(v)
Co
2
+
\text{Co}^{2+}
Co
2
+
(vi)
Lu
2
+
\text{Lu}^{2+}
Lu
2
+
(vii)
Mn
2
+
\text{Mn}^{2+}
Mn
2
+
(viii)
Th
4
+
\text{Th}^{4+}
Th
4
+
Q2
Exercises
Why are
Mn
2
+
\text{Mn}^{2+}
Mn
2
+
compounds more stable than
Fe
2
+
\text{Fe}^{2+}
Fe
2
+
towards oxidation to their +3 state?
Q3
Exercises
Explain briefly how +2 state becomes more and more stable in the first half of the first row transition elements with increasing atomic number?
Q4
Exercises
To what extent do the electronic configurations decide the stability of oxidation states in the first series of the transition elements? Illustrate your answer with examples.
Q5
Exercises
What may be the stable oxidation state of the transition element with the following
d
d
d
electron configurations in the ground state of their atoms :
3
d
3
3d^{3}
3
d
3
,
3
d
5
3d^{5}
3
d
5
,
3
d
8
3d^{8}
3
d
8
and
3
d
4
3d^{4}
3
d
4
?
Q6
Exercises
Name the oxometal anions of the first series of the transition metals in which the metal exhibits the oxidation state equal to its group number.
Q7
Exercises
What is lanthanoid contraction? What are the consequences of lanthanoid contraction?
Q8
Exercises
What are the characteristics of the transition elements and why are they called transition elements? Which of the
d
d
d
-block elements may not be regarded as the transition elements?
Q9
Exercises
In what way is the electronic configuration of the transition elements different from that of the non transition elements?
Q10
Exercises
What are the different oxidation states exhibited by the lanthanoids?
Q11
Exercises
Explain giving reasons:
(i)
Transition metals and many of their compounds show paramagnetic behaviour.
(ii)
The enthalpies of atomisation of the transition metals are high.
(iii)
The transition metals generally form coloured compounds.
(iv)
Transition metals and their many compounds act as good catalyst.
Q12
Exercises
What are interstitial compounds? Why are such compounds well known for transition metals?
Q13
Exercises
How is the variability in oxidation states of transition metals different from that of the non transition metals? Illustrate with examples.
Q14
Exercises
Describe the preparation of potassium dichromate from iron chromite ore. What is the effect of increasing pH on a solution of potassium dichromate?
Q15
Exercises
Describe the oxidising action of potassium dichromate and write the ionic equations for its reaction with:
(i)
iodide
(ii)
iron(II) solution and
(iii)
H
2
S
\text{H}_2\text{S}
H
2
S
Q16
Exercises
Describe the preparation of potassium permanganate. How does the acidified permanganate solution react with (i) iron(II) ions (ii)
SO
2
\text{SO}_2
SO
2
and (iii) oxalic acid? Write the ionic equations for the reactions.
Q17
Exercises
For
M
2
+
/
M
\text{M}^{2+}/\text{M}
M
2
+
/
M
and
M
3
+
/
M
2
+
\text{M}^{3+}/\text{M}^{2+}
M
3
+
/
M
2
+
systems the
E
o
E^o
E
o
values for some metals are as follows:
Cr
2
+
/
Cr
−
0.9
V
Cr
3
/
Cr
2
+
−
0.4
V
\text{Cr}^{2+}/\text{Cr} \quad -0.9 \text{ V} \qquad \text{Cr}^{3}/\text{Cr}^{2+} \quad -0.4 \text{ V}
Cr
2
+
/
Cr
−
0.9
V
Cr
3
/
Cr
2
+
−
0.4
V
Mn
2
+
/
Mn
−
1.2
V
Mn
3
+
/
Mn
2
+
+
1.5
V
\text{Mn}^{2+}/\text{Mn} \quad -1.2 \text{ V} \qquad \text{Mn}^{3+}/\text{Mn}^{2+} \quad +1.5 \text{ V}
Mn
2
+
/
Mn
−
1.2
V
Mn
3
+
/
Mn
2
+
+
1.5
V
Fe
2
+
/
Fe
−
0.4
V
Fe
3
+
/
Fe
2
+
+
0.8
V
\text{Fe}^{2+}/\text{Fe} \quad -0.4 \text{ V} \qquad \text{Fe}^{3+}/\text{Fe}^{2+} \quad +0.8 \text{ V}
Fe
2
+
/
Fe
−
0.4
V
Fe
3
+
/
Fe
2
+
+
0.8
V
Use this data to comment upon:
(i)
the stability of
Fe
3
+
\text{Fe}^{3+}
Fe
3
+
in acid solution as compared to that of
Cr
3
+
\text{Cr}^{3+}
Cr
3
+
or
Mn
3
+
\text{Mn}^{3+}
Mn
3
+
and
(ii)
the ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.
Q18
Exercises
Predict which of the following will be coloured in aqueous solution?
Ti
3
+
,
V
3
+
,
Cu
+
,
Sc
3
+
,
Mn
2
+
,
Fe
3
+
\text{Ti}^{3+}, \text{V}^{3+}, \text{Cu}^{+}, \text{Sc}^{3+}, \text{Mn}^{2+}, \text{Fe}^{3+}
Ti
3
+
,
V
3
+
,
Cu
+
,
Sc
3
+
,
Mn
2
+
,
Fe
3
+
and
Co
2
+
\text{Co}^{2+}
Co
2
+
. Give reasons for each.
Q19
Exercises
Compare the stability of +2 oxidation state for the elements of the first transition series.
Q20
Exercises
Compare the chemistry of actinoids with that of the lanthanoids with special reference to:
(i)
electronic configuration
(ii)
atomic and ionic sizes and
(iii)
oxidation state
(iv)
chemical reactivity.
Q21
Exercises
How would you account for the following:
(i)
Of the
d
4
d^4
d
4
species,
Cr
2
+
\text{Cr}^{2+}
Cr
2
+
is strongly reducing while manganese(III) is strongly oxidising.
(ii)
Cobalt(II) is stable in aqueous solution but in the presence of complexing reagents it is easily oxidised.
(iii)
The
d
1
d^1
d
1
configuration is very unstable in ions.
Q22
Exercises
What is meant by 'disproportionation'? Give two examples of disproportionation reaction in aqueous solution.
Q23
Exercises
Which metal in the first series of transition metals exhibits +1 oxidation state most frequently and why?
Q24
Exercises
Calculate the number of unpaired electrons in the following gaseous ions:
Mn
3
+
,
Cr
3
+
,
V
3
+
\text{Mn}^{3+}, \text{Cr}^{3+}, \text{V}^{3+}
Mn
3
+
,
Cr
3
+
,
V
3
+
and
Ti
3
+
\text{Ti}^{3+}
Ti
3
+
. Which one of these is the most stable in aqueous solution?
Q25
Exercises
Give examples and suggest reasons for the following features of the transition metal chemistry:
(i)
The lowest oxide of transition metal is basic, the highest is amphoteric/acidic.
(ii)
A transition metal exhibits highest oxidation state in oxides and fluorides.
(iii)
The highest oxidation state is exhibited in oxoanions of a metal.
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