d and f block Elements
Exam Duration: 45 Mins Total Questions : 30
Among the following, the compound that does not exist is
- (a)
K2TiO4
- (b)
K2TiF6
- (c)
TiO2
- (d)
TiCl4
The oxidation states shown by Ti is + 2, and + 4. The oxidation state of Ti in the given compounds is
K2TiO4 ⇾ 6, K2TiF6 ⇾ +4, TiO2 ⇾ 4,
and TiCl4 ⇾ +4
since, +6 oxidation state is not shown by Ti,
Hence, K2TiO4 does not exist.
Which of the following does not show any colour in solution?
- (a)
V3+
- (b)
Co2+
- (c)
Cr3+
- (d)
Sc3+
Colour is shown by the ions due to the presence o unpaired electrons. The outermost electronic configuration of various ion is
V3+=3d24so, Co2+ = 3d74So
Cr3+=3d34so, Sc3+=3do4so
Since, Sc3+ does not contain any unpaired electron, therefore, it will be colourless in solution.
Zinc does not exhibit variable valency due to
- (a)
presence of complete filled d-orbitals
- (b)
inert pair effect
- (c)
presence of 4s-orbitals
- (d)
None of the above
Zinc contains completely filled d-orbitals and exhibit stable electronic configuration, therefore it does not easily loose their electron and hence, does not exhibit variable valency.
Which of the following pair of compounds shows similar colour in aqueous medium?
- (a)
FeCl2 and MnCl2
- (b)
COCl2 and CuCl2
- (c)
VOCl2 and feCl2
- (d)
FeCl3 and CuCl2
Metal ions with same number of unpaired electrons exhibit same colour in their aqueous solution. In VOCl2, V is present as
V4+(3d1) and Cu as Cu2+(3d9) in CuCl2
Both possess same number of unpaired electrons in their 3d orbitals. Hence, show similar colour.
For d-block elements, the first ionisation potential is in the order of
- (a)
Zn
- (b)
V>Cr>Mn>Fe
- (c)
Zn>Fe>Cu>Cr
- (d)
Sc>Ti>V>Cr
Ionisation potential increases with increase in the number of electrons in the atomic orbital
Element | Sc | Ti | V | Cr | Mn | Fe | Co | Ni | Cu | Zn |
---|---|---|---|---|---|---|---|---|---|---|
IE_1, (kJ mol-1) | 631 | 656 | 650 | 653 | 717 | 762 | 758 | 736 | 745 | 909 |
Hence, the correct order is
Zn > Fe > Cu > Cr
The basicity of lanthanoid hydroxides, across the lanthanoid series
- (a)
decreases
- (b)
increases
- (c)
first decreases and then increases
- (d)
first increases and then decreases
On moving from let to right across the lanthanoid series, basicity of lanthanoid hydroxides decreases.
Among the following lanthanoid ions, the paramagnetic ion is
- (a)
Yb2+
- (b)
Eu2+
- (c)
Lu3+
- (d)
Ce4+
The valence shell electronic configuration of the given ions are
Yb = [Xe] 4f14 6s2 ⇒ Yb2+ = [Xe]4f14 ⇒ no unpaired e-
Eu = [Xe] 4f7 6s2 ⇒ Eu2+ = [Xe]4f7 ⇒ 7 unpaired e-
Lu = [Xe]4f14 5d1 6s2 ⇒ Lu3+ = [Xe]4f14 ⇒ no unpaired e-
Ce = [Xe]4f1 5d1 6s2 ⇒ Ce4+ = [Xe] ⇒ no unapired e-
Hence, Eu2+ is paramagneric as it contains 7 unpaired e-.
Which of the following ion act as an oxidising agent?
- (a)
Eu2+
- (b)
Np4+
- (c)
Sm2+
- (d)
Yb2+
The ions whose oxidation state changes from +4 to +3 act as an oxidising agent while those ions whose oxidation state changes from +2 to +3 tends to act as reducing agents. Hence Np4+ is an oxidising agent.
The lanthanoid contraction is related to
- (a)
atomic radii
- (b)
atomic as well as ionic radii, M3+
- (c)
valence electrons
- (d)
oxidation states
Lanthanoid contraction is related to both atomic and ionic radii, M3+
Lanthanoids and actinoids differ from each other because
- (a)
of the presence of partially filled outermost shells
- (b)
actinoids are radioactive in nature
- (c)
they show common oxidation state of +3
- (d)
both are known as inner transition elements
All lanthanoids except promethium are non-radioactive whereas all actinoids are radioactive in nature.
Actinoids possess
- (a)
variable valency
- (b)
12 elements
- (c)
all synthetic elements
- (d)
only short-lived isotopes
Actinoids show variable valency due to the presence of a small difference in the energies 5f, 6d and 7s orbitals.
When SO2 is passed through an acidified K2Cr2O7 solution, the oxidation state of sulphur changes from
- (a)
+4 to 0
- (b)
+4 to +2
- (c)
+4 to +6
- (d)
+6 to +4
When SO2 passes through acidified K2Cr2O7 solution, the following reactions take place
\(K_2Cr_2O_7+4H_2SO_4\rightarrow K_2SO_4+Cr_2(S_4)_3+4H_2O+3[0]\over [SO_2+[O]+H_2O\longrightarrow H_2SO_4]\times3\)
K2Cr2O7 + H2SO4 + 3SO2 ⟶ K2SO4 + Cr2(SO4)3 + H2O
In SO2, oxidation state of S is +4 but in \(SO_4^{2-},\) oxidation state changes to +6.
Among the following given electronic configuration of d-orbitals the electronic configuration showing highest magnetic moment is
- (a)
3d2
- (b)
3d5
- (c)
3d7
- (d)
3d8
The electronic configuration of 3d5 contains 5 unpaired electrons among all the given configurations, thus, shows highest magnetic moment.
A transition metal ion possess a magnetic moment of \(\sqrt{15}\)BM, the number of unpaired electrons present in this metal ion is
- (a)
1
- (b)
2
- (c)
3
- (d)
4
the magnetic moment is given by
\(\sqrt{n(n+2)}BM\)
where, n ➝ number of unpaired electrons
Therefore, \(\sqrt{n(n+2)}=\sqrt{15}\)
⇒ n(n+2)=15
⇒ n2 + 2n = 15
⇒ n2 + 2n - 15 = 0
(n + 5)(n - 3) = 0
n = 3
Identify the correct statement.
- (a)
Co3+ is most stable in octahedral complexes than tetrahedral
- (b)
Zn forms coloured complexes
- (c)
Compounds formed by d-block elements are generally ferromagnetic
- (d)
Osmium shows +6 oxidation state
Cobalt in +3 oxidation state, forms most stable octahedral complexes than tetrahedral
For the ions, Cu2+(3d9) and Cu+(3d10), the correct statement is
- (a)
Cu2+ is more stable than cu+
- (b)
Cu2+ is less stable than Cu+
- (c)
Cu2+ and Cu+ ions are equally stable
- (d)
Stability of Cu+ and Cu2+ depends on the nature of copper salts
Cu2+ ion is more stable than Cu+ ion. The stability of Cu2+(aq) rather than Cu+(aq) due to the much more negative \(\Delta_{hyd}H^o\) of Cu2+(aq) than Cu+(aq) which is more than compensation for the second ionisation enthalpy of Cu.
The purple colour of KMnO4 is due to
- (a)
resonance in MnO4- ion
- (b)
charge transfer
- (c)
ionic nature of KMnO4
- (d)
partially filled d-orbitals
Due to charge transfer because of the absence of unpaired electrons.
KMnO4 acts as oxidising agent in acidic medium. The number o moles of KmnO4 that will be needed to react with one mole of sulphide ions in acidic solution is
- (a)
\(2\over 5\)
- (b)
\(3\over 5\)
- (c)
\(4\over 5\)
- (d)
\(1\over 5\)
Around 2/5 moles of KMnO4 are required to react with one mole of S2- ions in acidic medium to produce 1 mole of S.
\({2\over5}MnO_4^-+S^{2-}+{16\over5}H^+\rightarrow{2\over 5}Mn^{2+}+{8\over 5}H_2O+S\)
The addition of acidified K2Cr2O7 solution to Sn2+ salts, causes a change of Sn2+ to
- (a)
Sn+
- (b)
Sn3+
- (c)
Sn4+
- (d)
Sn
When acidified K2Cr2O7 is added to Sn2+ salts, Sn2+ changes to Sn4+ through oxidation.
Although zirconium belongs to 4d transition series and Hafnium to 5d transition series even then, they show similar physical and chemical properties because .........
- (a)
both belongs to d-block
- (b)
both have same number of electrons
- (c)
both have similar atomic radius
- (d)
both belong to the same group of the periodic table
Zirconium and Hafnium shows similar properties due to the presence of similar atomic radii
The element with maximum number of oxidation states in their compounds is
- (a)
Eu
- (b)
La
- (c)
Gd
- (d)
Am
Eu, La and Gd belong to lanthanoids. Higher oxidation states are not possible in lanthanoids because of the large energy gap between 4f and 5d subshells. The element Am shows maximum number of oxidation states.
The incorrect statement in reference to 3d and 4f series element is
- (a)
3d elements show large number o oxidation states than 4f series elements
- (b)
energy difference between 3d and 4f-orbitals in very small
- (c)
Eu2+ is more stable than Ce2+
- (d)
paramagnetic character increases from Sc to Zn in 3d series.
In 3d-series paramagnetic character first increases from Sc to Mn due to increase in the number of unpaired electrons and then decreases from Fe to Cu.
Iron exhibits +2 and +3 oxidation states. Which of the following statements about iron is incorrect?
- (a)
Ferrous oxide is more basic in nature than the ferric oxide
- (b)
Ferrous compounds are relatively more ionic than the corresponding ferric compounds
- (c)
Ferrous compounds are less volatile than the corresponding ferric compounds
- (d)
Ferrous compounds are more easily hydrolysed than the corresponding ferric compounds
(a) FeO > Fe2O3 (basic) correct.
(b) FeCl2 > FeCl3 (ionic), larger the charge, greater the polarising power thus, greater the covalent nature. Thus, correct.
(c) Fe2+ salts are more ionic thus, less volatile than Fé3+ salts. Thus, correct.
(d) Greater the covalent nature, more easily they are hydrolysed. Thus, FeC13 is more hydrolysed than FeCl2. Thus, statement (d) is incorrect.
The outer electron configuration of Gd (Atomic number 64) is
- (a)
4f35d56s2
- (b)
4f8 5d0 6s2
- (c)
4f4 5f4 6s2
- (d)
4f7 5d1 6s2
Gd(64) All the electrons in 4f-orbital are unpaired, hence stable. Thus, Gd(64) has EC as [Xe]54 4f7 5d1 6s2.
Instead of [Xe]54 4f8 6s2
The correct order of \(E^o_{M^{2+}/M}\) values with negative sign for the four successive elements Cr, Mn, Fe and Co is
- (a)
Mn > Cr > Fe > Co
- (b)
Cr > Fe > Mn > Co
- (c)
Fe > Mn > Cr > Co
- (d)
Cr > Mn > Fe > Co
Usually across the first transition series, the negative values for standard electrode potential decrease except for Mn due to stable d5 configuration.
So correct order, Mn > Cr > Fe > Co
Large number of oxidation states are exhibited by the antinoids than those by the lanthanoids, the main reason being
- (a)
4f orbitals more diffused than the 5f orbitals
- (b)
lesser energy difference between 5f and 6d than between 4f and 5d-orbitals.
- (c)
more energy difference between 5f and 6d orbitals than between 4f and 5d orbitals
- (d)
more reactive nature of the actinoids than the lanthanoids
Lanthanoids [Xe] 4f1-14 5d0-1 6s2
Actinoids [Rn] 5f1-14 6d0-1 7s2
Lanthanoids and actinoids use core d and f-orbitals also to show higher oxidation state. As actinoids have comparatively low energy difference between f and show more oxidation states.
Cerium (Z=58) is an important member of the lanthanides. Which of the following statements about cerium is incorrect?
- (a)
The common oxidation states of cerium are +3 and +4
- (b)
The +3 oxidation state of cerium is more stable than the +4 oxidation state
- (c)
The +4 oxidation state of cerium is not known in solutions
- (d)
Cerium (IV) acts as an oxidising agent
+3 and +4 states are shown by Ce in aqueous solution
Of the following outer electronic configurations of atoms, the highest oxidation state is achieved by which one of them?
- (a)
(n-1)d8ns2
- (b)
(n-1)d5ns1
- (c)
(n-1)d3ns2
- (d)
(n-1)d5ns2
(n-1)d5ns2
What would happen, when solution of potassium chromate is treated with an excess of dilute nitric acid?
- (a)
Cr3+ and Cr2O72- are formed
- (b)
Cr2O72- and H2O are formed
- (c)
Cr2O42- is reduced to +3 state of Cr
- (d)
None of the above
\(2CrO_{ 4 }^{ 2- }+2H^{ + }\longrightarrow Cr_{ 2 }O_{ 7 }^{ 2- }+H_{ 2 }O\)