d and f Block Elements — Page 4 | JEE Chemistry

Q31

Which one of the following species is stable in aqueous solution?

A Cr2+

B Cu+

C MnO

_4^{3 - }

D MnO

_4^{2 - }

Correct Answer

Option D

Solution

MnO42− disproportionate as (in neutral or acidic solution) 3MnO42− + 4H+ → 2MnO42− + MnO2 + 2H2O

Q32

The oxide that shows magnetic property is :

A MgO

B SiO2

C Mn3O4

D Na2O

Correct Answer

Option C

Solution

Mn3O4 is paramagnetic due to presence of unpaired electrons.

Q33

The 'f' orbitals are half and completely filled, respectively in lanthanide ions : [Given : Atomic no. Eu, 63; Sm, 62; Tm, 69; Tb, 65; Yb, 70; Dy, 66]

A Eu2+ and Tm2+

B Sm2+ and Tm3+

C Tb4+ and Yb2+

D Dy3+ and Yb3+

Correct Answer

Option C

Solution

Tb $\to$ 4f9 6s2 Tb+4 $\to$ 4f7 Yb $\to$ 4f14 6s2 Yb+2 $\to$ 4f14 Hence, the pair Tb+4 and Yb+2 have half filled and completely filled f subshells respectively.

Q34

Consider the following reactions

\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7 \xrightarrow[-\mathrm{H}_2 \mathrm{O}]{\mathrm{KOH}}[\mathrm{~A}] \xrightarrow[-\mathrm{H}_2 \mathrm{O}]{\mathrm{H}_2 \mathrm{SO}_4}[\mathrm{~B}]+\mathrm{K}_2 \mathrm{SO}_4

The products

[A]

and

[B]

, respectively are :

A

\mathrm{K}_2 \mathrm{Cr}(\mathrm{OH})_6

and

\mathrm{Cr}_2 \mathrm{O}_3

B

\mathrm{K}_2 \mathrm{CrO}_4

and

\mathrm{Cr}_2 \mathrm{O}_3

C

\mathrm{K}_2 \mathrm{CrO}_4

and

\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7

D

\mathrm{K}_2 \mathrm{CrO}_4

and

\mathrm{CrO}

Correct Answer

Option C

Solution

$\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7 \xrightarrow[-\mathrm{H}_2 \mathrm{O}]{\mathrm{KOH}} \underset{\text{ [A] }}{\mathrm{K}_2 \mathrm{CrO}_4} \xrightarrow[-\mathrm{H}_2 \mathrm{O}]{\mathrm{H}_2 \mathrm{~S}_4} \underset{\text{ [B] }}{\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7}+\mathrm{K}_2 \mathrm{SO}_4$

Q35

Which of the following ions is the strongest oxidizing agent? (Atomic Number of

\mathrm{Ce}=58, \mathrm{Eu}=63, \mathrm{~Tb}=65, \mathrm{Lu}=71

)

A

\mathrm{Lu}^{3+}

B

\mathrm{Eu}^{2+}

C

\mathrm{Tb}^{4+}

D

\mathrm{Ce}^{3+}

Correct Answer

Option C

Solution

$\mathrm{Tb}^{4+}$ is strongest oxidising agent

Q36

The ore that contains the metal in the form of fluoride is :

A sphalerite

B magnetite

C malachite

D cryolite

Correct Answer

Option D

Solution

Magnetite $\to$ Fe3O4 Sphalerite $\to$ ZnS Cryolite $\to$ Na3AlF6 Malachite $\to$ CuCO3. Cu(OH)2

Q37

Calamine and Malachite, respectively, are the ores of :

A Nickel and Aluminium

B Zinc and Copper

C Copper and Iron

D Aluminium and Zinc

Correct Answer

Option B

Solution

Calamine $\Rightarrow$ ZnCO3 Malachite $\Rightarrow$ Cu(OH)2 .

CuCO3 Note : ( Remember all those ores names.

Any one of those can be asked in the exam.)

Oxides Ores : (1) ZnO - Zincite (2) Fe2O3 - Haematite (3) Fe3O4 - Magnetite (FeO + Fe2O3 mixture) (4) Fe2O3 .

3H2O - Limonite (5) MnO2 - Pyrolusite (6) Cu2O - Cuprite or Ruby Copper (7) TiO2 - Rutile (8) FeCr2O4 - Chromite (FeO + Cr2O3) (9) FeTiO3 - Illmenite (FeO + TiO2) (10) Na2B4O7 .

10H2O - Borax or Tincal (11) U3O8 - Pitch Blende (12) SnO2 - Tin Stone or Cassiterite (13) Ca2B6O11 .

5H2O - Colemanite (2 Cao + 3 B2O3) (14) Al2O3 .

2H2O - Bauxite (15) Al2O3 .

H2O - Diaspore (16) Al2O3 - Corundum Sulphides Ores : (1) ZnS - Zinc Blende or Sphalerite (2) PbS - Galena (3) Ag2S - Argentite or Silver Glance (4) HgS - Cinnabar (5) Cu2S - Chalcocite or Copper glance (6) CuFeS2 - Copper pyrites or Chalco pyrites (Cu2S + Fe2S3 mixture) (7) FeS2 - Iron pyrites or Fool's Gold (8) 3Ag2S .

Sb2S2 - Pyrargyrite or ruby silver Halides Ores : (1) NaCl - Rock Salt (2) KCl - Sylvine (3) Na3AlF6 - Cryolite [3NaF + AlF6] (4) CaF2 - Fluorspar (5) KCl .

MgCl2 .

6H2O - Carnalite (6) AgCl - Horn Silver Carbonates Ores : (1) CaCO3 - Limestone (2) MgCO3 - Magnesite (3) CaCO3 .

MgCO3 - Dolomite (4) ZnCO3 - Calamine (5) PbCO3 - Cerrusite (6) FeCO3 - Siderite (7) CuCO3 .

Cu(OH)2 or Cu2CO3(OH)2 - Malachite or Basic Copper Carbonates (8) 2 CuCO3 .

Cu(OH)2 - Azurite Sulphates Ores : (1) CuSO4 .

2H2O - Gypsum (2) MgSO4 .

7H2O - Epson Salt (3) Na2SO4 .

10 H2O - Glauber's Salt (4) PbSO4 - Anglesite (5) ZnSO4 .

7H2O - White Vitriol (6) FeSO4 .

7H2O - Green Vitriol (7) CuSO4 .

5H2O - Blue Vitriol or Chalcanthite Nitrate Ores : (1) KNO3 - Indian Saltpetre (2) NaNO3 - Chile Saltpetre Arsenides Ores : (1) NiAs - Kupfernickel (2) NiAsS - Nickel glance

Q38

Given below are two statements : Statement I : According to Ellingham diagram, any metal oxide with higher

\Delta

G

^\circ

is more stable than the one with lower

\Delta

G

^\circ

. Statement II : The metal involved in the formation of oxide placed lower in the Ellingham diagram can reduce the oxide of a metal placed higher in the diagram. In the light of the above statements, choose the most appropriate answer from the options given below :

A Both Statement I and Statement II are correct.

B Both Statement I and Statement II are incorrect.

C Statement I is correct but Statement II is incorrect.

D Statement I is incorrect but Statement II is correct.

Correct Answer

Option D

Solution

Ellingham diagram is plot of

\Delta

G vs T.

The criterion for the feasibility of a thermal reduction is that at a given temperature Gibbs energy change of a reaction must be negative.

The change in Gibbs energy,

\Delta

G for any process at any specified temperature is given by the equation

\Delta

G =

\Delta

H - T

\Delta

S where

\Delta

H = enthalpy change and

\Delta

S = entropy change According to the ellingham diagram, any metal oxide with higher

\Delta

G° has a tendency of getting reduced by the metal whose metal oxide has lower value of

\Delta

G°.

Q39

A red solid is insolvable in water. However it becomes soluble if some

K{\rm I}

is added to water. Heating the red solid in a test tube results in liberation of some violet colored fumes and droplets of a metal appear on the cooler parts of the test tube. The red solid is :

A

Hg{{\rm I}_2}

B

HgO

C

P{b_3}{O_4}

D

{\left( {N{H_4}} \right)_2}C{r_2}{O_7}

Correct Answer

Option A

Solution

When

K{\rm I}

is added to mercuric iodide it dissolve in it and form complex.

\mathop {Hg{{\rm I}_2}}\limits_{red,solid(inso{\mathop{\rm lub}} le)} \,\, + \,\,\,K{\rm I} \to \mathop {{K_2}\left[ {Hg{{\rm I}_4}} \right]}\limits_{(soluble)}

On heating

Hg{{\rm I}_2}

decomposes as

Hg{{\rm I}_2}\,\,\,\,Hg\,\,\rightleftharpoons\, + \mathop {{{\rm I}_2}}\limits_{(violetvapours)}

Q40

The radius of La3+ (Atomic number of La = 57) is 1.06 Å. Which one of the following given values will be closest to the radius of Lu3+ (Atomic number of Lu = 71) ?

A 1.60 Å

B 1.40 Å

C 0.85 Å

D 1.60 Å

Correct Answer

Option C

Solution

Ionic radili

\propto {1 \over z}

Thus,

{{{z_2}} \over {{z_1}}} \Rightarrow {{1.06} \over {\left( {Ionic\,\,\,radii\,\,\,of\,\,L{u^{3 + }}} \right)}} = {{71} \over {57}}

\Rightarrow \,\,\,

Ionic radii of

L{u^{3 + }} = 0.85\,\mathop A\limits^ \circ