d and f Block Elements — Page 8 | NEET Chemistry

Q71

Which of the following ore is concentrated using group 1 cyanide salt ?

A Sphalerite

B Malachite

C Siderite

D Calamine

Correct Answer

Option A

Solution

The chemical formulas of given ore in options are as follows Sphalerite ore : ZnS Calamine ore : ZnCO3 Siderite ore : FeCO3 Malachite ore : Cu(OH)2.

CuCO3 Sphalerite ore containing ZnS is concentrated using group is cyanide salt (NaCN) as a depressant by froth flotation method.

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

Q72

Given below are two statements : Statement I : Sphalerite is a sulphide or of zinc and copper glance is a sulphide ore of copper. Statement II : It is possible to separate two sulphide ores by adjusting proportion of oil to water or by using 'depressants' in a forth flotation method. Choose the most appropriate answer from the options given below :

A Statement I is true but Statement II is false.

B Both Statement I and Statement II are true.

C Statement I is false but Statement II is true.

D Both Statement I and Statement II are false.

Correct Answer

Option B

Solution

sphalerite-ZnS, copper glance - Cu2S two sulphide ores can be separated by adjusting proportions of oil to water or by using 'Depressants'.

Q73

Match with .tg .tg

List - I		List - II
(A)	Concentration of gold ore	(I)	Aniline
(B)	Leaching of alumina	(II)	NaOH
(C)	Froth stabiliser	(III)	SO $_2$
(D)	Blister copper	(IV)	NaCN

A (A) - (IV), (B) - (III), (C) - (II), (D) - (I)

B (A) - (IV), (B) - (II), (C) - (I), (D) - (III)

C (A) - (III), (B) - (II), (C) - (I), (D) - (IV)

D (A) - (II), (B) - (IV), (C) - (III), (D) - (I)

Correct Answer

Option B

Solution

Gold is concentrated by cyanidation Leaching of alumina is done by NaOH Froth stabiliser is aniline Blister copper has condensed SO2 on the surface

Q74

Given below are two statements : Statement I : In froth floatation method of rotating paddle agitates the mixture to drive air out of it. Statement II : Iron pyrites and generally avoided for extraction of iron due to environmental reasons. In the light of the above statements, choose the correct answer from the options given below :

A Statement I is true but Statement II is false

B Statement I is false but Statement II is true

C Both Statement I and Statement II are true

D Both Statement I and Statement II are false

Correct Answer

Option B

Solution

Statement I is false because the rotating paddle in froth floatation method agitates the mixture to generate froth and not to drive air out of it.

Statement II is true because iron is commercially extracted from haematite ore and not from iron pyrites to minimize environmental pollution.

Q75

The metal ion (in gaseous state) with lowest spin-only magnetic moment value is :

A V2+

B Ni2+

C Cr2+

D Fe2+

Correct Answer

Option B

Solution

Valence shell configuration Unpaired electrons V2+ 3d34s0 n = 3 Ni2+ 3d84s0 n = 2 Cr2+ 3d44s0 n = 4 Fe2+ 3d64s0 n = 4 Since Ni2+ has least number of unpaired electrons.

Hence Ni2+ will have lowest spin only magnetic moment Value.

Q76

The correct set of ions (aqueous solution) with same colour from the following is:

A

\mathrm{V}^{2+}, \mathrm{Cr}^{3+}, \mathrm{Mn}^{3+}

B

\mathrm{Ti}^{4+}, \mathrm{V}^{4+}, \mathrm{Mn}^{2+}

C

\mathrm{Sc}^{3+}, \mathrm{Ti}^{3+}, \mathrm{Cr}^{2+}

D

\mathrm{Zn}^{2+}, \mathrm{V}^{3+}, \mathrm{Fe}^{3+}

Correct Answer

Option A

Solution

(1) $\mathrm{V}^{2+}$ (Violet), $\mathrm{Cr}^{3+}$ (Violet), $\mathrm{Mn}^{3+}$ (Violet) (2) $\mathrm{Zn}^{2+}$ (Colourless), $\mathrm{V}^{3+}$ (Green), $\mathrm{Fe}^{3+}$ (Yellow) (3) $\mathrm{Ti}^{4+}$ (Colourless), $\mathrm{V}^{4+}$ (Blue), $\mathrm{Mn}^{2+}$ (Pink) (4) $\mathrm{Sc}^{3+}$ (Colourless), $\mathrm{Ti}^{3+}$ (Purple), $\mathrm{Cr}^{2+}$ (Blue)

Q77

Statement I : Leaching of gold with cyanide ion in absence of air / O2 leads to cyano complex of Au(III). Statement II : Zinc is oxidized during the displacement reaction carried out for gold extraction. In the light of the above statements, choose the correct 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

Leaching of gold with cyanide ion is done in presence of air/O2 leading to cyano complex [Au(CN)2]– where Au is in +1 oxidation state.

4Au(s) + 8CN–(aq) + 2H2O(aq) + O2(g)

\longrightarrow 4\left[\mathrm{Au}(\mathrm{CN})_{2}\right]_{\mathrm{aq}}^{-}+4 \mathrm{OH}^{-}

\begin{aligned} 2\left[\mathrm{Au}(\mathrm{CN})_{2}\right]_{(\mathrm{aq})}^{-} &+\mathrm{Zn}(\mathrm{s}) \\ & \longrightarrow\left[\mathrm{Zn}(\mathrm{CN})_{4}\right]_{(\mathrm{aq})}^{2-}+2 \mathrm{Au}(\mathrm{s}) \end{aligned}

Zinc is oxidised from (0) to +2 oxidation state during displacement reaction carried out for gold extraction.

Q78

The correct statement is :

A leaching of bauxite using concentrated NaOH solution gives sodium aluminate and sodium silicate

B the Hall-Heroult process is used for the production of aluminium and iron

C pig iron is obtained from cast iron

D the blistered appearance of copper during the metallurgical process is due to the evolution of CO2

Correct Answer

Option A

Solution

(A) Leaching of bauxite : Al2O3.

H2O + NaOH $\to$ Na[Al(OH)4] + Na2SiO3 So, option (A) is correct.

(B) Hall Heroult’s process is used for aluminium only not for iron.

So, option (B) is wrong.

(C) From Blast Furnace, at the end we get pig iron and in pig iron percentage of carbon is high and after reducing the carbon percantage we get cast iron.

So we can say cast iron is obtained from pig iron.

So, option (C) is wrong.

(D) In Bessemer converter following reaction happens : Cu2S + Air $\to$ Cu2O + SO2 Cu2O + Cu2S $\to$ Cu + SO2 So we can say, Appearance of Blister copper is due to evolution of SO2 gas.

$\therefore$ Option (D) is wrong.

Q79

How do we differentiate between Fe3+ and Cr3+ in group III?

A by taking excess of NH4OH solution

B by increasing

NH_4^+

ion concentration

C by decreasing OH- ion concentration

D both (b) and (c)

Correct Answer

Option B

Solution

FeCl3 + 3NH4OH $\to$ Fe(OH)3 ↓(reddish brown) + 3NH4Cl CrCl3 + 3NH4OH $\to$ Cr(OH)3 (Bluish green) + 3NH4Cl

Q80

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