MCQ Questions for Class 12 Engineering Chemistry The D-And F-Block Elements Quiz 1

The ionic charges on chromate ion and dichromate ion respectively is:

0%
$-2, -2$
0%
$-3, -2$
0%
$-2, -4$
0%
$-4, -2$

Explanation

Chromate salts contain the chromate anion,

$CrO_4^{2−}$ with -2 ionic charge.

Dichromate salts contain the dichromate anion,

$Cr_2O_7^{2-}$ with -2 ionic charge.

They are oxoanions of chromium in the +6 oxidation state.

Hence, option

$A$ is correct.

1407832_1676880_ans_4cdd8848197c4361a1bc10645cbefecd.png

Which element is a transition metal?

0%
melting point in $^{o}C$ - 98; density in $g/{cm}^{3}$ - 1.0; colour of oxide - white
0%
melting point in $^{o}C$ - 328; density in $g/{cm}^{3}$ - 11.3; colour of oxide - yellow
0%
melting point in $^{o}C$ - 651; density in $g/{cm}^{3}$ - 1.7; colour of oxide - white
0%
melting point in $^{o}C$ - 1240; density in $g/{cm}^{3}$ - 7.4; colour of oxide - black

Explanation

$\text{A transition metal must have high melting point with low density.}$

$\text{So option C is correct.}$

$E _ { 1 },\ E _ { 2 }$ and

$E _ { 3 }$ are the emf values of the three galvanic cells respectively.
(a)

$Zn\left| Zn_{ { 1M } }^{ { +2 } } \right| \left| Cu_{ { 0.1M } }^{ { +2 } } \right| Cu$
(b)

$Zn\left| Zn_{ { 1M } }^{ { +2 } } \right| \left| Cu_{ { 1M } }^{ { +2 } } \right| Cu$
(c)

$Zn\left| Zn_{ { 0.1M } }^{ { +2 } } \right| \left| Cu_{ { 1M } }^{ { +2 } } \right| Cu$
Which one of the following is true?

0%
$\mathrm { E } _ { 2 } > \mathrm { E } _ { 3 } > \mathrm { E } _ { 1 }$
0%
$\mathrm { E } _ { 3 } > \mathrm { E } _ { 2 } > \mathrm { E } _ { 1 }$
0%
$\mathrm { E } _ { 1 } > \mathrm { E } _ { 2 } > \mathrm { E } _ { 3 }$
0%
$\mathrm { E } _ { 1 } > \mathrm { E } _ { 3 } > \mathrm { E } _ { 2 }$

Which of the following pair has similar magnetic moment?

0%
$Cr^{3+}, Mn^{3+}$
0%
$Fe^{3+}, Mn^{2+}$
0%
$Fe^{2+}, Mn^{2+}$
0%
$Ni^{2+}, Co^{2+}$

Explanation

The magnetic moment is given as

$\mu=\sqrt{n(n+2)}$

where,

$n=$ number of unpaired electrons

$Fe^{3+}$ and

$Mn^{2+}$ have an equal number of 5 unpaired electrons.

Thus, they have a similar magnetic moment.

$Gd\ (64)$ has _________ unpaired electrons with sum of spin __________.

0%
$7, 3.5$
0%
$8, 3$
0%
$6, 3$
0%
$8, 4$
0%
$9, 3.5$

Explanation

The element

$Gd(Z=64)$ show electronic configuration

$=[Xe]_{54}\cdot 4f^7, 5d^1, 6s^2$ .

As it has

$8$ - unpaired electrons (

$4f^7$ and

$5d^1$ ) and its sum of spin

$=8\times \dfrac{1}{2}=4$ .

Amphoteric behaviour is shown by the oxides of:

0%
$Al$ and $Ca$
0%
$Pb$ and $Ba$
0%
$Cr$ and $Mg$
0%
$Sn$ and $Zn$

Explanation

Amphoteric oxides can behave as an acid as well as the base. They react with both acids and bases to form salts. Tin oxide although doesn't dissolve in water but it is amphoteric in nature. Zinc oxide is also amphoteric in nature.

$ZnO+HCl \rightarrow ZnCl_2+H_2O$

$ZnO+NaOH \rightarrow Na_2ZnO_2+H_2O$

$SnO_2+HCl \rightarrow SnCl_4+H_2O$

$SnO_2+NaOH+H_2O \rightarrow Na_2[Sn(OH)_6]$

Hence, option D is correct.

The first IE of lithium is

$5.4$ eV and first electron affinity of

$Cl$ is

$3.6$ eV. The value of

$\Delta H$ for the reaction

$Li_{(g)} + Cl_(g) \rightarrow Li^{+}_{(g)} + Cl^{-} _{(g)}$ , is (in eV) :

0%
$+1.8$
0%
$+ 2.8$
0%
$- 2.8$
0%
$+ 9$

Explanation

When lithium becomes a cation we give energy to the system. Hence energy is increased in the system and vice versa for chlorine i.e energy is released.

Hence energy is decreased from the system on the whole energy change is

$5.4-3.6=1.8.$

Potassium dichromate can be prepared by:

0%
heating $Na_{2}Cr_2O_{7}$ solution with $KCl$ solution and then cooling.
0%
heating powdered chromite ore with quicklime in the presence of air
0%
heating $K_{2}CrO_{4}$ with sulphuric acid
0%
both $A$ and $C$

Explanation

Potassium dichromate is usually prepared by the reaction of potassium chloride on sodium dichromate.

$Na_{2}Cr_{2}O_{7}+2KCl \rightarrow K_{2}Cr_{2}O_{7}+2NaCl$

It can also be prepared by heating

$K_{2}CrO_{4}$ with

$H_{2}SO_{4}$ .

$2K_{2}CrO_{4}+2H^+ \rightarrow K_{2}Cr_{2}O_{7}+2K^++H_{2}O$

Hence, option D is correct.

The magnetic moment of

$[Cu(NH_{3})_{4}]^{2+}$ was found to be 1.73 B.M. The number of unpaired electrons in the complex is:

0%
0
0%
1
0%
2
0%
3

Explanation

Magnetic moment of a complex having n-unpaired electrons is given by:

$\sqrt{n(n+2)}$ , where

$n$ is the number of unpaired electrons.

$\sqrt{n(n+2)}= 1.73$

$\therefore$

$n=1$ .

$AgCl$ and

$NaCl$ are colourless.

$NaBr$ and

$NaI$ are also colourless but

$AgBr$ and

$AgI$ are coloured. This is due to:

0%
$Ag^+$ polarizes $Br^-$ and $I^-$
0%
$Ag^+$ has unpaired d - orbital
0%
$Ag^+$ depolarizes $Br^-$ and $I^-$
0%
None is correct

Explanation

According to Fajan's rule, smaller the size of cation and larger the size of anion, the greater is the covalent character of the ionic compound.

$AgBr$ and

$AgI$ ,

$Ag^+$ being smaller in size it polarizes

$Br^-$ and

$I^-$ due to which they are colored.

Hence, the correct option is (A).

Which of the following types of metals forms the most efficient catalysts

0%
Alkali metals
0%
Alkaline earth metals
0%
Transition metal
0%
All of these

Which of the following statements is not true in regard to transition elements?

0%
They readily form complex compounds
0%
They show variable valency
0%
All their ions are colourless
0%
Their ions contain partially filled d -electron levels

Explanation

"All their ions are colourless" this sentence is false because they are

$90\%$ coloured and only few are colourless.

Transitional elements are named transition elements because their characters are

0%
in between s and p - block elements
0%
like that of p and d - block elements
0%
they are members of I – A group
0%
they are like inactive elements

Which forms coloured salts?

0%
Metals
0%
Non-metals
0%
p-block elements
0%
Transitional elements

Which of the following ions having the following electronic structure would have a maximum magnetic moment?

0%
$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^23d^{3}$
0%
$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^23d^{5}$
0%
$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^23d^{7}$
0%
$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^23d^{9}$

Explanation

Magnetic moment =

$\sqrt{n(n+2)}$ , where n is no. of unpaired electrons.

Higher the number of unpaired electrons, higher is the magnetic moment.

Number of unpaired electrons are maximum in option B (5 unpaired electrons).

Option A and C: 3 unpaired electrons.

Option D: 1 unpaired electron.

Titanium shows the magnetic moment of 1.73 BM. in its compound. What is the oxidation number of

$Ti$ in the compound?

0%
+1
0%
+4
0%
+3
0%
+2

Explanation

Magnetic moment =

$\sqrt{n(n+2)}$ = 1.73 B.M.

$\therefore$ Unpaired electrons,

$n$ = 1

Now, configuration of

$Ti$ =

$[Ar] 4s^2 3d^2$ .

Hence, the oxidation number must be +3.

If the colours of salts of transition elements are due to the presence of unpaired electrons in the transition metal ions, which of the following ions will be colourless in aqueous solution.

0%
$Ti^{3+}$
0%
$Ti^{4+}$
0%
$Fe^{2+}$
0%
$Fe^{3+}$

Explanation

$Ti^{4+} \rightarrow 3d^0 4s^0$ ions will be colourless in aqueous solution as it has no unpaired electrons.

The correct order of atomic radii is:

0%
$Yb^{3+}< Pm^{3+}< Ce^{3+}< La^{3+}$
0%
$Ce^{3+}< Yb^{3+}< Pm^{3+}< La^{3+}$
0%
$Yb^{3+}< Pm^{3+}< La^{3+}< Ce^{3+}$
0%
$Pm^{3+}< La^{3+}< Ce^{3+}< Yb^{3+}$

Explanation

Ionic radii decrease as we move across the lanthanide series due to lanthanide contraction.

As all ions are in

$+3$ oxidation state, ionic radii will follow the trend of atomic radii:

$Yb^{3+}< Pm^{3+}< Ce^{3+}< La^{3+}$

(Atomic number of

$La = 57, Ce = 58, Pm = 61, Yb = 70$ )

Hence, option A is correct.

Iron sheets are covered with a layer of zinc i.e., galvanized mainly to:

0%
harden the surface
0%
increase the surface
0%
prevent action of water only
0%
prevent action of oxygen and water

Which of the following belongs to actinoid series of elements?

0%
Nd
0%
U
0%
Sm
0%
Au

In the dichromate anion,

0%
4 $Cr-O$ bonds are equivalent
0%
6 $Cr-O$ bonds are equivalent
0%
all $Cr-O$ bonds are equivalent
0%
all $Cr-O$ bonds are non-equivalent

Explanation

In the dichromate anion

$(Cr_2O_7)^{2-}$ , 6

$Cr-O$ terminal bonds are equivalent due to resonance.

Which compound is volatile on heating?

0%
$MgCl_{2}$
0%
$HgCl_{2}$
0%
$ZnCl_{2}$
0%
none of these

Explanation

$Hg$ metal is present in liquid state, hence

$HgCl_{2}$ is volatile in nature.

Which of the following ions has the least magnetic moment?

0%
$Cu^{2+}$
0%
$Ni^{2+}$
0%
$Co^{3+}$
0%
$Fe^{2+}$

Explanation

Since

$Cu^{2+}$ ions has only one unpaired electron so it has the least magnetic moment.

1640613_1758163_ans_63213190503a4d06a5f5f98f192f0bbd.JPG

Which of the following is diamagnetic transitional metal ion?

0%
$Ni^{2+}$
0%
$Zn^{2+}$
0%
$Co^{2+}$
0%
$Cu^{2+}$

Explanation

$Zn^{2+} - [Ar]3d^{10}$ has no unpaired electrons hence, diamagnetic in nature.

Which of the following is not true for transition metals?

0%
They are malleable and ductile
0%
They have high boiling and melting points
0%
They crystallize with body centred cubic and hexagonal close-packed structures only
0%
They show variable oxidation states although not always

The elements belonging to the first transition series have an atomic number from

0%
19 to 37
0%
22 to 32
0%
24 to 30
0%
21 to 30

Which is not true for transition elements?

0%
They are all metals
0%
They show variable valency
0%
They form coloured ions
0%
They do not form co-ordinate compounds

Cuprous ion is colourless while cupric ion is coloured because

0%
Both have half filled p and d-orbitals
0%
Cuprous ion has incomplete d-orbital and cupric ion has a completely filled d-orbital
0%
Both have unpaired electrons in the d-orbitals
0%
Cuprous ion has a completely filled d-orbital and cupric ion has an incomplete d-orbital

Which of the following will give green hydrated ion?

0%
$Fe^{2+}$
0%
$Ni^{2+ }$
0%
(A) and (B) both
0%
$V^{3+}$

Explanation

$Fe^{2+}$ and

$Ni^{2+}$ both will give green hydrated ion.

$Fe^{2+}$ shows

0%
Paramagnetism
0%
Diamagnetism
0%
None of these
0%
Ferromagnetism

Explanation

$Fe^{2+}$ ion have 4 unpaired electron so it is paramagnetic.

The first ionisation potential of

$N, P, O$ and

$S$ are in the order of:

0%
$S > P < O > N$
0%
$N > O > P > S$
0%
$N > O < P > S$
0%
$N < O < P < S$

Explanation

Moving left to right within a period or upward within a group, the first ionization energy generally increases with a few discrepancies (aluminum and nitrogen group).

Nitrogen group to oxygen group, I.P. decreases instead of increasing because of the stable half-filled configuration of nitrogen family.

$N(1400) >O(1313)>P(1011)>S(999)$

The Lanthanoids contraction relates to:

0%
atomic radii
0%
atomic as well as $M^{3+}$ radii
0%
valence electrons
0%
oxidation states.

Explanation

The Lanthanoids contraction relates to atomic as well as

$M^{3+}$ radii.

The atomic and ionic radii (

$M^{3+}$ ions) of Lanthanide elements decrease with increase in atomic number. This effect is called Lanthanoid contraction. This is due to poor shielding of 4f electrons.

Which of the following cannot form oxo ion?

0%
$PuO_{2}^{+}$
0%
$CeO_{2}^{+}$
0%
$UO_{2}^{2+}$
0%
$NpO_{2}^{+}$

Explanation

$\displaystyle CeO_{2}^{+}$ is not possible as cerium cannot form oxo ion.

Lanthanoids cannot form oxo ions while actinides can form oxo ions like

$\displaystyle UO^+, UO_2^+, PuO_2^{2+}$ .

For which of the following transition metal ion is shown highest magnetic moment having outer electronic configuration

0%
$3d^1$
0%
$3d^8$
0%
$3d^5$
0%
$3d^7$

Explanation

Magnetic moment depends upon the number of unpaired electrons.

$3d^5$ will show the highest magnetic moment as it has 5 unpaired electrons.

Which of the following ions is coloured?

0%
$Cu^+$
0%
$Cu^{2+}$
0%
$Ti^{4+}$
0%
$V^{5+}$

Explanation

$Cu^{2+} \rightarrow [Ar]3d^9 4s^0$

$Cu^{2+}$ ion is coloured due to the presence of 1 unpaired electron in d-orbitals.

Which one of the following properties is not of transition elements?

0%
Colour
0%
Paramagnetism
0%
Fixed valency
0%
None of the above

Number of $Cr-O$ bonds in dichromate ion $(Cr_{2}O_{7}^{2-})$ is:

0%
6
0%
7
0%
8
0%
4

Explanation

From structure, it is clear that it has

$8\ Cr-O$ bond, out of which

$6\ Cr-O$ bonds are equal.

IP values of Sc, Y and La are in the order:

0%
Sc > Y > La
0%
Sc < Y < La
0%
Sc = Y = La
0%
La > Sc > Y

Explanation

IP values of Sc, Y and La are in the order

$\displaystyle Sc > Y > La$

On moving down the group, the IP values decreases as the effective nuclear charge decreases due to poor shielding by inner electrons.

Which statement is not true ?

0%
Zn is a transition metal.
0%
Ag is coinese metal.
0%
Density of Osmium is the greatest.
0%
All of the above.

Which of the following metals make the most efficient catalyst?

0%
Transition
0%
Alkali
0%
Alkaline earth
0%
Coloured metals

Which belongs to the actinides series?

0%
$Ce$
0%
$Cf$
0%
$Ca$
0%
$Cs$

The 3d-metal ions are paramagnetic in nature because

0%
They are reducing agents
0%
They form coloured salt
0%
They have one or more paired s-electrons
0%
They have one or more unpaired d-electrons

Which of the following metals absorbs hydrogen?

0%
K
0%
Al
0%
Zn
0%
Pd

Explanation

At 350K and 1 atm pressure, 1 unit volume of Pd absorbs 900 unit volume of

$H_2$ gas. This property of Pd makes it a good catalyst.

The correct order of ionic radii of

$Y^{3+}, La^{3+}, Eu^{3+}$ and

$Lu^{3+}$ is:
(Atomic number of Y=39, La=57, Eu=63, Lu=71)

0%
$Lu^{3+} < Eu^{3+} < La^{3+} < Y^{3+}$
0%
$La^{3+} < Eu^{3+} < Lu^{3+} < Y^{3+}$
0%
$Y^{3+} < La^{3+} < Eu^{3+} < Lu^{3+}$
0%
$Y^{3+} < Lu^{3+} < Eu^{3+} < La^{3+}$

Explanation

Due to lanthanide contraction size of lanthanides ions decreases from

$La^{3+}$ to

$Lu^{3+}$ .

so order is

$Y^{3+} < Lu^{3+} < Eu^{3+} < La^{3+}$

Hence, the correct option is

$D$ .

The aqueous solution of the salt will colored in the case of:

0%
$Zn{({NO}_{3})}_{2}$
0%
$Li{NO}_{3}$
0%
$Co{({NO}_{3})}_{2}$
0%
$Cr{Cl}_{3}$

Explanation

$Co^{2+}$ =

$3d^7$

$Cr^{3+}$ =

$3d^3$

$Co^{2+}$ and

$Cr^{3+}$ will have unpaired electrons and hence are expected to have aqueous solution of the salt colored.

Which of the following represents the correct order of the properties indicated?

0%
${Ni}^{2+}> {Cr}^{2+}> {Fe}^{2+}> {Mn}^{2+}$ (size)
0%
$Sc> Ti> Cr> Mn$ (size)
0%
${Ni}^{2+}< {Co}^{2+}< {Fe}^{2+}< {Mn}^{2+}$ (unpaired electron)
0%
${Cr}^{3+}> {Cr}^{2+}$ (magnetic moment)

The color of the transition metal ions is due to:

0%
$d-d$ transition
0%
charge transfer
0%
change in the geometry
0%
none

In which of the following. tendency towards formation of coloured ions is maximum

0%
s-block elements
0%
d-block elements
0%
p-block elements
0%
f-block elements

What is/are true statement?

0%
Ions of $d$ -block elements are colored due to $d-d$ transition
0%
Ions of $f$ -block elements are colored due to $f-f$ transtition
0%
${ \left[ Sc{ \left( { H }_{ 2 }O \right) }_{ 6 } \right] }^{ 3+ },{ \left[ Ti{ \left( { H }_{ 2 }O \right) }_{ 6 } \right] }^{ 4+ }$ are colored complexes.
0%
${Cu}^{+}$ is colorless ion.

Explanation

$Cu^+$ is colourless because it doesn't contain any electrons which can absorb light. .

${ \left[ Sc{ \left( { H }_{ 2 }O \right) }_{ 6 } \right] }^{ 3+ }$ ,

$Sc^{3+}$ is

$d^0$ system and hence colorless.

Hence,option C is incorrect.

Magnetic moment

$\sqrt{35}$ is true for which of the following pair :

0%
$Co^{+2}, Fe^{+2}$
0%
$Fe^{+3}, Mn^{+2}$
0%
$Co^{+3}, Cr^{+2}$
0%
$Fe^{+2}, Mn^{+2}$

Explanation

Magnetic moment =

$\sqrt{35}$

$\sqrt{n(n+2)}= 35$

Therefore, n= 5

$Fe^{3+}, Mn^{2+}- [Ar]3d^5$

CBSE Questions for Class 12 Engineering Chemistry The D-And F-Block Elements Quiz 1 - MCQExams.com

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Practice Class 12 Engineering Chemistry Quiz Questions and Answers

CBSE Questions for Class 12 Engineering Chemistry The D-And F-Block Elements Quiz 1 - MCQExams.com

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Practice Class 12 Engineering Chemistry Quiz Questions and Answers

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