MCQ Questions for Class 12 Engineering Chemistry The D-And F-Block Elements Quiz 14

Transition metals show paramagnetic :

0%
due to characteristic configuration
0%
high lattice energy
0%
due to variable oxidation states
0%
due to unpaired electrons

Match List-I with List -II and select the correct answer using codes given ahead in the lists:

List-I Metal ions	List-II Magnetic moments (B.M)
$Cr^{3+}$	$\sqrt{35}$
$Fe^{2+}$	$\sqrt{30}$
$Ni^{2+}$	$\sqrt {24}$
$Mn^{2+}$	$\sqrt{15}$
	$\sqrt 8$

0%
$A-1, B-3, C-5, D-4$
0%
$A-2, B-3, C-5, D-1$
0%
$A-4, B-3, C-5, D-1$
0%
$A-4, B-5, C-3, D-1$

Wilkinson's catalyst contains :

0%
rhodium
0%
iron
0%
aluminium
0%
cobalt

The catalysic activity of transition elements and their compounds is described to:

0%
their chemical reactivity
0%
their magnetic behaviour
0%
their unfilled $d-$ orbital
0%
their ability to adopt multiple oxidation states and their complexing ability.

Select the correct statements :

0%
Diamond is hard while graphite is soft and slippery
0%
The degree of co valency in the following compounds runs as $HgX_2 > CdX_2 > ZnX_2$
0%
$ZnS$ is white, $CdS$ is yellow, while $HgS$ is black
0%
Diamond is soft while graphite is hard

Which of the following sulphides is yellow in colour?

0%
$CuS$
0%
$CdS$
0%
$ZnS$
0%
$CoS$

Explanation

Alkali and alkaline earth metal sulphides are colourless.

Heavy metal sulphides are unusually deeply coloured.

Both

$CuS$ and

$CoS$ are black coloured,

$ZnS$ is bluish white.

$CdS$ is yellow in colour.

Hence the correct option is

$(B)$ .

The statement that is not correct for the periodic classification of elements is:

0%
The properties of elements are the periodic function of their atomic numbers.
0%
Non - metallic elements are lesser in number than metallic elements.
0%
The first ionisation energies of elements along a period do not vary in a regular manner with increase in atomic number.
0%
For transition elements the d subshells are filled with electrons monotonically with increase in atomic number.

Which of the following compounds is (are) coloured due to charge transfer spectra and not due to

$d-d$ transition?

0%
$KMnO_4$
0%
$K_2CrO_4$
0%
$CrO_3$
0%
All of these

On heating chromite

$(FeCr_2O_4)$ with

$Na_2CO_3$ in air, the following product is obtained:

0%
$Na_2CrO_4$
0%
$Na_2Cr_2O_7$
0%
$FeO$
0%
$Fe_3O_4$

Number of moles of

$K_2Cr_2O_7$ radius by

$1$ mole of

$Sn^{2+}$ is:

0%
$1/6$
0%
$2/3$
0%
$1/3$
0%
$1$

Explanation

The balanced chemical reactions (ionic reactions) for reduction of

$K_2Cr_2O_7$ by

$Sn^{2+}$ are;

$Cr_2O_7^{2-}+14H^++6e^-\rightarrow 2Cr^{3+}+7H_2O$

$3(Sn^{2+}\rightarrow Sn^{4+}+2e^-)$

Balances net equation:

$3Sn^{2+}+Cr_2O_7^{2-}+14H^+\rightarrow 3Sn^{4+}+2Cr^{3+}+7H_2O$

Thus,

According to the balanced reaction,

$1$ mole of

$Cr_2O_7^{2-}$ will be reduced by

$3$ moles of

$Sn^{2+}$

Thus,

$1$ mole of

$Sn^{2+}$ will be reduced

$=\dfrac 13$ moles of

$Cr_2O_7^{2-}$

Hence the correct answer is option C.

Which of the following are paramagnetic?

0%
$[Fe(CN)_6]^{4-}$
0%
$Ni(CO)_4$
0%
$[NiCl_4]^{2-}$
0%
$[CoF_6]^{3-}$

Predict the magnetic nature of

$A$ and

$B$ :

0%
Both are diamagnetic
0%
Both are paramagnetic
0%
$A$ is paramagnetic and $B$ is diamagnetic
0%
$A$ is diamagnetic and $B$ is paramagnetic

Which of the following sulphides is yellow?

0%
$ZnS$
0%
$CdS$
0%
$NiS$
0%
$PbS$

Explanation

$ZnS\rightarrow{White}$

$CdS\rightarrow{Yellow}$ {Option (B) is correct.}

$NiS\rightarrow{Brown}$

$PbS\rightarrow{Black}$

Consider the following statements and arrange in the order of true/false as given in the codes.

$S_{1}$ : Both

$\left [ Co\left ( ox \right )_{3} \right ]^{3-}$ and

$\left [ CoF_{6} \right ]^{3-}$ are paramegnetic.

$S_{2}:CoCl_{3}3NH_{3}$ complex is non-conducing.

$S_{3}$ : The number of possible isomers for the complex

$\left [ Pt\left ( NO_{2} \right )\left ( py \right )\left ( OH \right )\left ( NH_{3} \right ) \right ]$ is six.

$S_{4}$ : The oxidation state of iron in brown ring complex

$\left [ Fe\left ( H_{2}O \right )_{5}NO^{+} \right ]SO_{4}$ is +II where NO is

$NO^{+}$

0%
F T T F
0%
T T T T
0%
F T T F
0%
T T T F

Explanation

$S_1:[CoF_6]^{3−}\text{ is paramagnetic with 5 unpaired electrons but }[Co(ox)_3]^{3−}\text{ is diamagnetic as all electrons}$ $\text{are paired.}$
$S_2:\text{ It exists as }[Co(NH_3)_3Cl_3],\text{ neutral molecule.}$
$S_3:\text{ It is a correct statement. It shows linkage and geometrical isomerism.}$
$S_4: [Fe(+I)(H_2O)_5NO^+]SO^{2−}_4$

Option C is correct.

Which of the following complexes is / are paramagnetic?

0%
$\left [ Mn\left ( CN_{6} \right ) \right ]^{3-}$
0%
$\left [ Cr\left ( NH_{3} \right )_{6} \right ]^{3+}$
0%
$\left [ Fe\left ( CN \right )_{6} \right ]^{4-}$
0%
$\left [ Co\left ( CN \right )_{6} \right ]^{3-}$

Which of the following statements is correct ? (I) Anions of both (B) and (C) are diamagnetic and have tetrahedral geometry (II) Anions of both (B) and (C) are paramagnetic and have tetrahedral geometry (III) Anions of (B) is paramagnetic and that of (C) is diamagnetic but both have tetrahedral geometries (IV) Green coloured compound (B) in a neutral or acidic medium disproportionates to give (C) and (D)

0%
I and II only
0%
II and III only
0%
II and IV only
0%
III and IV only

Which of the following types of metal make the most efficient catalysts?

0%
Alkali metal
0%
Transition metal
0%
Alkali-earth metals
0%
Radioactive metals

Which of the following pair of compounds is expected to exhibit same colour in aqueous solution ?

0%
$FeCl_{2},CuCl_{2}$
0%
$VOCl_{2},CuCl_{2}$
0%
$VOCl_{2},FeCl_{2}$
0%
$FeCl_{2},MnCl_{2}$

Titanium shows magnetic moment of 1.73 B M in its compound . What is the oxidation state of titanium in the compound ?

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

Consider the following statements and arrange in the order of true/false as given in the codes.

$S_{1}$ : The IUPAC name of the compound

$\left [ Cr\left ( NH_{3} \right )_{5} \left ( NCS \right )\right ]\left [ ZnCl_{4} \right ]$ is pentaamminethiocyanato-N-chromate (III) tetraachlorozincate (II).

$S_{2}: CoSO_{4}$ is paramagnetic and coloured.

$S_{3}:\left [ Co\left ( NH_{3} \right )_{4}\left ( NO_{2} \right )_{2} \right ]NO_{3}$ shows ionisation, linkage and geometrical isomerism.

$S_{4}$ : The C-O bond length in the complex,

$\left [ Fe\left ( CO \right )_{5} \right ]$ is same as that found in carbon monoxide itself.

0%
F T T F
0%
T T T T
0%
F T T F
0%
T T T F

Fe, Co and Ni have valuable catalytic properties in process involving

0%
Organic compound
0%
Oxidation
0%
Hydrogenation
0%
Compounds of hydrogen

Which has the maximum ferromagnetic character?

0%
Fe
0%
Co
0%
Ni
0%
Pt

Which of the following may be colourless?

0%
$Cr^{3+}$
0%
$Cu^{+}$
0%
$Fe^{3+}$
0%
$Cu^{2+}$

Explanation

$Cu^{+}$ may be colourless due to completely filled d-orbitals.
1654367_1758861_ans_24e4cb61aca9475aa9d8368b58187141.png

Which of the following species is expected to show the highest magnetic moment? (At. No.: Cr = 24, Mn = 25, Co = 27, Ni = 28, Cu =29)

0%
$Cr^{2+}$
0%
$Mn^{2+}$
0%
$Cu^{2+}$
0%
$Co^{2+}$
0%
$Ni^{2+}$

Explanation

Highest magnetic moment depends upon number of unpaired electron since.

$Cr^{2+} = [Ar]3d^4 4s^0 , \quad Mn^{2+} = [Ar]3d^5 4s^0$

$Cu^{2+} = [Ar]3d^9 4s^0,\quad Co^{2+} = [Ar]3d^7 4s^0 ,\quad Ni^{2+} = [Ar]3d^8 4s^0$

$Mn^{2+}$ contain maximum number of unpaired electron i.e. 5.

The 3d metal ions form coloured compounds because the energy corresponding to the following lies in the visible range of electromagnetic spectrum

0%
free energy change of complex formation by 3d metal ions
0%
d-d transition of 3d electrons
0%
heat of hydration of 3d metal ions
0%
ionisation energy of 3d metal ions

Which one of the following characteristics of the transition metals is associated with their catalytic activity?

0%
Variable oxidation states
0%
High enthalpy of atomization
0%
Paramagnetic behaviour
0%
Colour of hydrated ions

The magnetic moment of a metal ion of first transition series is 2.83 BM. Therefore it will have unpaired electrons

0%
6
0%
4
0%
3
0%
2

Explanation

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

where, n. no. of unpaired electron.

$2.83 = \sqrt { n(n+2) }$

$n(n+2) = 8$

$n^2 +2n - 8 = 0$

$n = 2$

Which of the following trivalent ion has the largest atomic radii in the lanthanide series?

0%
$La$
0%
$Ce$
0%
$Pm$
0%
$Lu$

Explanation

Lanthanum is the first and repesentative element of Lanthanide series and size decreases with increase in atomic number. So,

$La$ has the largest atomic radii.

A copper salt is isomorphic with

$ZnSO_4$ , the salt will be

0%
paramagnetic
0%
diamagnetic
0%
ferromagnetic
0%
none

Explanation

$ZnSO_4 \rightarrow Zn^{2+} + SO^{2-}_4$

Isomorphic with

$Zn^{2+} \approx Cu^{2+}$

$Cu^{2+} \rightarrow [Ar]3d^9 - 1$ unpaired electron.

$\therefore$ Paramagnetic in nature

Effective magnetic moment of

$Sc^{3+}$ ion is

0%
1.73
0%
0
0%
5.92
0%
2.83
0%
3.87

Explanation

Magnetic moment,

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

Where

$n =$ number of unpaired electrons

For

$Sc^{3+} = [Ar]3d^0 , \quad n = 0 , \quad \therefore \mu = 0$

Which one of the following ions is colourless?

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

Explanation

$Cu^+$ ion is colourless as it has no unpaired electrons.

$Cu^+ - [Ar]3d^{10} 4s^0$

Which of the following ions has the highest magnetic moment?

0%
$Ti^{3+}$
0%
$Sc^{3+}$
0%
$Mn^{2+}$
0%
$Zn^{2+}$

Explanation

$Ti^{3+} \rightarrow [Ar]3d^1 4s^0 ; \ Sc^{3+} \rightarrow [Ar]3d^0$

$Mn^{2+} \rightarrow [Ar]3d^5 4s^0; \ Zn^{2+} \rightarrow [Ar]3d^{10} 4s^0$

$Mn^{2+} \rightarrow$ number of unpaired electrons

$= 5.$

So it has maximum magnetic moment according to the formula

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

Chloride of which of the following element is coloured?

0%
Ag
0%
Hg
0%
Zn
0%
Co

Explanation

Chloride of Co element is coloured.

$CoCl_3 - Co^{3+} - [Ar]3d^6 4s^0 \to$ 4 unpaired electrons. So, it will be coloured.

In nitroprusside ion, the iron and

$NO$ exist as

$Fe^{II}$ and

$NO^+$ rather than

$Fe^{III }$ and

$NO$ . These forms can be differentiated by

0%
Estimating the concentration of iron
0%
Measuring the concentration of $CN^-$
0%
Measuring the solid state magnetic moment
0%
Thermally decomposing the compound

Explanation

The existence of

$Fe^{2+}$ and

$NO^+$ in Nitroprusside ion

$[Fe(CN)_5NO]^{2-}$ can be established by measuring the magnetic moment of the solid compound which should correspond to

$(Fe^{2+} = 3d^6 )$ four unpaired electrons.

On adding excess of

$NH_3$ solution to

$CuSO_4$ solution, the dark blue colour is due to

0%
$[ Cu(NH_3)_4] ^{2+}$
0%
$[ Cu(NH_3)_2]^{2+}$
0%
$[ Cu(NH_3)]^+$
0%
None of the above

Explanation

On adding excess of

$NH_3$ solution to

$CuSO_4$ solution, the dark blue colour is due to formation of

$[ Cu(NH_3)_4] ^{2+}$ ion.

$CuSO_4 + 4NH_3 \xrightarrow{aqueous} [Cu(NH_3)_4]^{2+}(aq)+ SO^{2-}_4(aq)$

Which of the following pair will have effective magnetic moment equal?

0%
$Cr^{3+}$ and $Mn^{2+}$
0%
$Cr^{2+}$ and $Fe^{2+}$
0%
$V^{2+}$ and $Sc^{3+}$
0%
$Ti^{2+}$ and $V^{2+}$

Explanation

$Cr^{2+}$ and

$Fe^{2+ }$ will have an effective magnetic moment equal since they have the same number of unpaired electrons.

$Cr^{2+} - [Ar]3d^4 \to$ 4 unpaired electrons

$Fe^{2+} - [Ar]3d^6\to$ 4 unpaired electrons

On heating

$Mn(OH)_2$ with

$PbO_2$ and conc.

$HNO_3$ pink colour is obtained due to the formation of

0%
$KMnO_4$
0%
$HMnO_4$
0%
$Pb(MnO_4 )_2$
0%
$PbMnO_4$

Explanation

Reaction of

$Mn(OH)_2$ with

$PbO_2$ and Conc.

$HNO_3$ :

2Mn(NO₃)₂ + 5PbO₂ + 6HNO₃ → 2HMnO₄ + 5Pb(NO₃)₂ + 2H₂O

The Pink colour is obtained due to the formation of

$HMnO_4$ .

Hence, Option "B" is the correct answer.

Which of the following weighs less when weighed in magnetic field?

0%
$VCl_3$
0%
$ScCl_3$
0%
$TiCl_3$
0%
$FeCl_3$

Explanation

$ScCl_3 \rightarrow Sc^{3+} + 3Cl^-$

$ScCl_3$ has no unpaired electron so will show diamagnetic character and will be repelled, so will weigh less.

1660544_1759881_ans_660511bdee394e8680d336c3b30ac183.png

Which of the following is more paramagnetic?

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

Explanation

$Fe^{3+} \to [Ar]3d^5\to$ having 5 unpaired electrons have the highest number of unpaired electrons so it will be more paramagnetic.

Which of the following reagents can be used for the given reaction ?

0%
$i. D_2O / D_3O^\bigoplus \,ii. Cl_2 + AcOH \,iii. NaBH_4 / H_2O$
0%
$i. Cl_2 + AcOH \,ii. D_2O \,iii. LAH / H_2O$
0%
$ii. D_2O \,iii. HgCl_2 / CdCO_3 / H_2O$
0%
$i. Base (PhLi), \,ii. HgCl_2 / CdCO_3-H_2O \, iii. D_2O$

Explanation

The

$(C=O)$ group is protected by converting into cyclic thioacetal and then an organometallic base like

$PhLi$ is used to generate carbanion followed by treatment with

$D_2O$ to incorporate

$D$ . Finally, the aldehyde is regenerated.

Hence, Option "C" is the correct answer.

1788316_1769561_ans_4bb6d09b53fa421880d6d6777dde3597.png

Pick out wrong combination

0%
$Fe^{+2}\rightarrow Haemoglobin$
0%
$Mg^{2+}\rightarrow Photosynthesis$
0%
$Se^{2+}\rightarrow Kreb \ Cycle$
0%
$CO^{+2}\rightarrow Vitamin \ B-12$

Explanation

Iron atom in the Haemoglobin of blood is in the +2 Oxidation state. ie., Iron is present as

$Fe^{2+}$ .

$\text{Mg2+ is the central atom of the chlorophyll molecule,}$ and fluctuations in its levels in the chloroplast regulate the activity of key photosynthetic enzymes. Relatively little is known of the proteins mediating Mg2+ uptake and transport in plants.

Cobalt is also an essential trace element for humans, and is found at the centre of vitamin B12 and a range of other co-enzymes called cobalamins.

and, in there is no involvement of

$Se^{2+}$ in kreb cycle. Thus, wrong combination is C.

Which of the following has maximum magnetic moment?

0%
${V}^{3+}$
0%
${Cr}^{3+}$
0%
${Fe}^{3+}$
0%
${C}^{3+}$

Which of the following is diamagnetic?

0%
${Cu}^{2+}$
0%
${Zn}^{2+}$
0%
${Cr}^{2+}$
0%
${Ti}^{2+}$

Transition metals are not characterized by :

0%
fixed valency
0%
coloured compound
0%
high melting and boiling points
0%
tendency to form complexes

The calculated spin only magnetic moment of

$Cr^{2+}$ ion is

0%
$4.90 BM$
0%
$5.92 BM$
0%
$2.84 BM$
0%
$3.87 BM$

Explanation

Electronic configuration of the ion:

$Cr^{2+} \Rightarrow [Ar] 4s^0 3d^4$

$n=4$

Spin only magnetic moment

$\Rightarrow \sqrt {n(n+2)} = \sqrt {4 \times (4+2)}=4.9 BM$

Option A is correct.

1830540_1881111_ans_5b78cdfd74d64678b39f2e6ca3b118e0.png

CBSE Questions for Class 12 Engineering Chemistry The D-And F-Block Elements Quiz 14 - 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 14 - MCQExams.com

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Practice Class 12 Engineering Chemistry Quiz Questions and Answers

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