MCQ Questions for Class 12 Engineering Chemistry General Principles And Processes Of Isolation Of Elements Quiz 2

Which of the following is not a method of extraction of metals?

0%
Enrichment of ore
0%
Refining
0%
Magnetic separation
0%
None of the above

Which of the following technique uses high temperature to convert ore into raw metals?

0%
Pyrometallurgy
0%
Hydrometallurgy
0%
Both a and b
0%
None of above

Which of the following is a physical mean for concentration of ore?

0%
Using sodium hydroxide
0%
Using electrolysis
0%
Froth flotation method
0%
None of above

What is the most common type of electrometallurgical processes to obtain pure metal?

0%
Electro-refining
0%
Electrowinning
0%
Both a and b
0%
Oxidation

Aluminium foils are used for:

0%
wrapping chocolates and food stuff
0%
to prepare hydrogen
0%
both $A$ and $B$
0%
none of these

Explanation

Aluminium foils are impermeable to oxygen and water; thus are used for wrapping chocolates and foodstuff.

It can be used for the preparation of hydrogen using the reaction of aluminium foil with a sodium hydroxide solution.

$2Al + 2NaOH + 6H_2O \rightarrow 2Na[Al(OH)_4] + 3H_2\uparrow$

Hence, the correct option is

$\text{C}$

Which of the following pairs is incorrect?

0%
Gneiss - Metamorphic
0%
Rock salt - Sedimentary
0%
Dolerite - Igneous
0%
Dolomite - Igneous

When

$ZnS$ and

$PbS$ minerals are present together, then

$NaCN$ is added to separate them in the froth flotation process as a depressant, because:

0%
$Pb(CN)_2$ precipitated while no effect on $ZnS$
0%
$ZnS$ forms soluble complex $Na_2 Zn(CN)_4$
0%
$PbS$ forms soluble complex $Na_2Pb(CN)_4$
0%
both $(a)$ and $(b)$

Explanation

$NaCN$ prevents

$ZnS$ from forming the froth by reacting with it to from complex

$Na_2[Zn(CN)_4]$ and acts as a depressant. While it does not prevent

$PbS$ from forming froth and both the ores can easily be separated.

______ metal generally occurs in free state.

0%
Sodium
0%
Platinum
0%
Magnesium
0%
Potassium

Explanation

Platinum is a chemical element with the symbol Pt and atomic number

$78$ . It is a dense, malleable, ductile, highly

$unreactive$ , precious, silverish-white transition metal. Since it is noble metal it is found in free state.

The earthy impurities present in the mineral are called:

0%
flux
0%
slag
0%
gangue
0%
refractory material

The final product in solvay process is:

0%
$Na_{2}CO_{3}$
0%
$Na_{2}CO_{3}.10H_{2}O$
0%
$Na_{2}CO_{3}.H_{2}O$
0%
$Na_{2}CO_{3}.8H_{2}O$

Explanation

The final product obtained in Solvay process (also known as ammonia soda process) is

${ Na }_{ 2 }C{ O }_{ 3 }\cdot 10{H }_{ 2 }O$ .

$2NaHCO_3 \rightarrow Na_2CO_3 + H_2O + CO_2$

Method used for the concentration of sulphide ore is :

0%
hand picking
0%
froth floatation
0%
magnetic separation
0%
leaching

The olive oil used in froth floatation process is called :

0%
frothing agent
0%
collecting agent
0%
conditioning agent
0%
lubricating agent

The extraction of metal from the ore is:

0%
an oxidation process
0%
a reduction process
0%
a hydration process
0%
a neutralisation process

Explanation

Extraction of metal from the ore is a reduction process as in this process, metal ion gets reduced to metals.

Extraction of iron from ore haematite:

$3 Fe_2O_3 + CO \rightarrow 2 Fe_3O_4 + CO_2$

$Fe_3O_4 + CO \rightarrow 3Fe + 4 CO_2$

+3, -2 0

Option B is correct

Match Column 1 with Column 2:

Column 1	Column 2
A. Mond's process	$1.\ Cr_{2}O_{3}+2Al\xrightarrow{\triangle}2Cr+Al_{2}O_{3}$
B. van Arkel process	$2.\ TiCl_{4}+2Mg \xrightarrow{\triangle}Ti+2MgCl_{2}$
C. Thermite process	$3.\ Ni(CO)_{4} \xrightarrow{\triangle}Ni+4CO$
D. Kroll's process	$4.\ ZrI_{4} \xrightarrow{\triangle}Zr+2I_{2}$

0%
A - 1; B - 2; C - 3; D - 4
0%
A - 2; B - 4; C - 3; D - 1
0%
A - 3; B - 2; C - 1; D - 4
0%
A - 3; B - 4; C - 1; D - 2

Explanation

$A :$ Mond Process is used for purifying Nickel.

$Ni+4CO\overset{300K}{\rightarrow}Ni(CO)_{4}\overset{450K}{\rightarrow}Ni+4CO$

$B :$ Van Arkel Method is used for obtaining ultra-pure metals Ti, Zr, etc.

Impure Metal +

$I_{2}{\rightarrow}$ Metal Iodide

$\xrightarrow{Heat}$ Pure Metal +

$I_{2}$

$C :$ Thermite process is used for refining chromium.

$Cr_{2}O_{3}+2Al\overset{\Delta }{\rightarrow}2Cr+Al_{2}O_{3}$

$D :$ Kroll method is also used for Titanium refining.

$TiCl_{4}+2Mg\overset{\Delta }{\rightarrow}Ti+2MgCl_{2}$

Generally sulphide ores are concentrated by which of the following process?

0%
Hand picking
0%
Washing with water
0%
Leaching
0%
Froth floatation

The collecting agent in froth floatation process is:

0%
sodium ethyl xanthate
0%
pine oil
0%
lime
0%
water

Explanation

Collectors either chemically bond (chemisorption) on a hydrophobic mineral surface, or adsorb onto the surface through physisorption. Collectors increase the natural hydrophobicity of the surface, increasing the separability of the hydrophobic and hydrophilic particles. The collecting agent in froth floatation process is sodium ethyl xanthate.

Pine oil is also added in froth floatation but as frother.

Hence, the correct option is

$\text{A}.$

Liquation process is used for the concentration of which ore?

0%
Stibinite
0%
Tinstone
0%
Limestone
0%
Haematite

Explanation

Stibnite (antimonite) is a sulfide mineral with the formula

$Sb_2S_3$ . It is concentrated by liquation process.

It was formerly used for extracting antimony minerals from ore.

Separating silver from copper with the use of lead as a solvent, and refining tin.

Option A is correct.

Natron is a mineral whose formula represented by:

0%
$Na_{2}CO_{3}.H_{2}O$
0%
$Na_{2}CO_{3}.10H_{2}O$
0%
$Na_{2}SO_{4}.H_{2}O$
0%
$Na_{2}SO_{4}.7H_{2}O$

Explanation

Natron is a mixture of sodium carbonate decahydrate and 17% sodium bicarbonate. Small quantities of sodium chloride and sodium sulfate are also present.

$Na_{2}CO_{3}.10H_{2}O$ is the formula for Natron.

Option B is correct.

100% copper is obtained from crude copper by :

0%
zone refining method
0%
electrorefining
0%
liquation
0%
poling

Liquation method is used to refine which of the following crude metal?

0%
Silver
0%
Lead
0%
Mercury
0%
Copper

Which one of the following is used in the extraction of aluminium by electrolytic process?

0%
$Al_{2}O_{3}$
0%
$Al(OH)_{3}$
0%
$AlCl_{3}$
0%
$Al_{2}(SO_{4})_{3}$

Explanation

In the metallurgy of aluminium, purified

$Al_2O_3$ is mixed with

$Na_3AlF_6$ or

$CaF_2$ which lowers the melting point of the mix and brings conductivity.

$2Al_2O_3 + 6C → 4Al + 6CO$

This process of electrolysis is widely known as Hall-Heroult process.

Option A is correct.

Aluminium is obtained by the electrolysis of pure

$Al_{2}O_{3}$ , dissolved in:

0%
alumina
0%
bauxite
0%
cryolite and flourspar
0%
feldspar

Explanation

Aluminium is obtained by the electrolysis of pure alumina

$(Al_{2}O_{3})$ dissolved in cryolite

$(Na_3AlF_6)$ and fluorspar

$(CaF_2)$ . Cryolite and fluorspar lower the melting point of the mixture and increase electrical conductivity.

Which of the following metal is refined by distillation method?

0%
Zinc
0%
Iron
0%
Tin
0%
Copper

Explanation

Fractional distillation process utilizes the boiling point difference between metal and that of impurity. Using this process, crude zinc containing

$Cd, Fe$ and

$Pb$ as impurities can be refined.

Zone refining method is used for refining:

0%
$Al$
0%
$Ge$
0%
$Cu$
0%
$Fe$

Explanation

Zone refining is based upon fractional crystallization as the impurity prefers to stay in the melt and on solidification only pure metals solidifies on the surface of the melt.
Metals like

$Si, Ge$ and

$Ga$ of high purity are purified by this method.

In the extraction of aluminium the electrolyte is:

0%
fused cryolite with felspar
0%
fused cryolite with fluorspar
0%
pure alumina in molten cryolite with fluorospar
0%
pure alumina with bauxite and molten cryolite

Explanation

In the extraction of aluminium by electrolytic process alumina

$Al_2O_3$ is used along with fluorspar and cryolite in molten state.

In the extraction of aluminium by electrolytic process, cryolite is added to ________.

0%
lower the melting point of alumina
0%
increase the electrical conductivity
0%
minimise the anode effect
0%
remove impurities from alumina

Carbon cannot be used to reduce :

0%
$ZnO$
0%
$SnO_{2}$
0%
$Fe_{2}O_{3}$
0%
$Al_{2}O_{3}$

Explanation

Carbon is used to reduce

$ZnO$ ,

$Fe_2O_3$ and

$SnO_2$ above a certain temperature but it is not used for alumina as carbon lies above aluminium in Ellingham diagram.

Which of the following technique is used in the manufacture of aluminium from bauxite?

0%
Reduction with magnesium
0%
Reduction with coke
0%
Electrolytic reduction
0%
Reduction with iron

The formula of the most abundant salt of sodium in nature is:

0%
$NaNO_{3}$
0%
$NaCl$
0%
$Na_{2}CO_{3}$
0%
$Na_{2}SO_{4}$

In the Castner's process of extraction of sodium, the cathode is:

0%
iron rod
0%
nickel rod
0%
copper rod
0%
graphite rod

The metal obtained in the Pidgeon process is:

0%
$Na$
0%
$Mg$
0%
$Ca$
0%
$Al$

Explanation

The Pidgeon process is one of the methods of magnesium metal production via a silicothermic reaction.

$Si(s) + 2MgO(s) \rightarrow SiO_2(s) + 2Mg(g)$

Option B is correct.

The solubility of impurities in a metal in molten and solid states is different. This is principle involved in the refining of a metal by which of the following methods?

0%
Poling
0%
Liquation
0%
Zone refining
0%
Electrolysis

Identify the reaction during electrolytic reduction of alumina at cathode.

0%
$2H_{2}O_{2}\rightarrow O_{2}+4H^{+}+4e^{-}$
0%
$3F^{-}\rightarrow 3F+3e^{-}$
0%
$Al^{+3}+3e^{-}\rightarrow Al$
0%
$2H^{+}+2e^{-}\rightarrow H_{2}$

Explanation

During electrolytic reduction of Alumina,

the reaction at cathode is

$Al^{+3}+3e^{-}\rightarrow Al$ .

Option C is correct.

Cryolite is used in the electrolytic extraction of aluminium, because ___________ .

0%
it dissolves alumina
0%
it dissolves sodium
0%
it dissolves aluminium fluoride
0%
it decreases the solubility

Explanation

In the extraction of aluminium by electrolytic process, alumina

$Al_2O_3$ is used along with fluorspar and cryolite. Cryolite reduces the melting temperature of the mixture, and also act as solvent to help dissolve

$Al_2O_3$ .

In the Castner process for the extraction of sodium, the anode is made of:

0%
copper
0%
iron
0%
sodium
0%
nickel

The froth floatation process is used for the concentration of:

0%
ore having low density
0%
ore having magnetic nature
0%
ore having high density
0%
ore having water soluble gangue

Chile salt petre is the nitrate mineral of :

0%
potassium
0%
sodium
0%
calcium
0%
lithium

Explanation

Chile salt petre is a nitrate salt of sodium. Its formula is

$NaNO_3$ .

The cathode used in the electrolytic cell during aluminium extraction is made of ____________.

0%
aluminium
0%
carbon Iining
0%
iron
0%
steel

ASSERTION: In froth floatation process, sodium ethyl xanthate is used as a collector.
REASON: Sulphide ores are water soluble.

0%
If both assertion and reason are CORRECT, and the reason is the CORRECT explanation of the assertion.
0%
If both assertion and reason are CORRECT, but the reason is NOT the CORRECT explanation of the assertion.
0%
If assertion is CORRECT but reason is INCORRECT.
0%
If assertion is INCORRECT but reason is CORRECT.

Ellingham diagram represents the change in:

0%
$G$ with temperature
0%
$H$ with temperature
0%
$G$ with pressure
0%
$G-T S$ with temperature

Explanation

Ellingham diagram represents the change in free energy

$(\Delta G)$ with temperature.

An Ellingham diagram is a graph showing the temperature dependence of the stability for compounds. This analysis is usually used to evaluate the ease of reduction of metal oxides and sulphides.

The diagrams are useful in predicting the conditions under which an ore will be reduced to its metal. The analysis is thermodynamic in nature and ignores reaction kinetics. Thus, processes that are predicted to be favourable by the Ellingham diagram can still be slow.

Option A is correct.

Which one of the following ores is best concentrated by froth-floatation method?

0%
Magnetite
0%
Cassiterite
0%
Galena
0%
Malachite

Explanation

Galena (

$PbS$ ) is best concentrated by a froth-floatation method.
This method is used for the concentration of sulphide ores such as galena (

$PbS$ ), zinc blende (

$ZnS$ ) and copper pyrite

$(CuFeS_2)$ .

Hence, the correct option is

$C$

The method of zone refining of metals is based on the principle of:

0%
greater mobility of the pure metal than that of impurity
0%
higher melting point of the impurity than that of the pure metal
0%
greater noble character of the solid metal than that of the impurity
0%
greater solubility of the impurity in the molten state than in the solid state

Molecular formula of Glauber salt is:

0%
$CuSO_{4}.5H_{2}O$
0%
$MgSO_{4}.7H_{2}O$
0%
$Na_{2}SO_{4}.10H_{2}O$
0%
$FeSO_{4}.7H_{2}O$

Explanation

Glauber salt is a colourless crystalline solution of

$Na_{2}SO_{4}.10H_{2}O$ .

Froth floatation process for the concentration of sulphide ores is an illustration of the practical application of:

0%
adsorption
0%
absorption
0%
sedimentation
0%
coagulation

ASSERTION:

$CuFeS_{2}$ is concentrated by froth floatation method.
REASON:

$CuFeS_{2}$ is the main ore of copper.

0%
If both assertion and reason are CORRECT, and reason is the CORRECT explanation of the assertion
0%
If both assertion and reason are CORRECT, but reason is NOT the CORRECT explanation of the assertion
0%
If assertion is CORRECT but reason is INCORRECT
0%
If assertion is INCORRECT but reason is CORRECT

Explanation

Chief ore of copper is copper pyrite (

$CuFeS_{2}$ ). It is a sulphide ore and sulphide ores are concentrated by froth flotation method.

Which is not a mineral of aluminium?

0%
Anhydrite
0%
Bauxite
0%
Corundum
0%
Diaspore

Explanation

Anhydrite: anhydrous

$CaSO_4$

Bauxite:

$AlO_x (OH)_{(3-2x)}$

Diaspore:

$Al_2 O_3 .H_2 O$

Corundum:

$Al_2 O_3$

Option A is correct.

The common metal present in german silver, bell metal and brass is :

0%
Fe
0%
Cu
0%
Zn
0%
Sn

Which one of the following statements is incorrect?

0%
In the aluminothermite process, aluminium acts as reducing agent.
0%
Lead is extracted from its chief ore by both carbon reduction and self-reduction.
0%
Zinc is extracted from its chief ore by carbon reduction.
0%
Extraction of gold involves the leaching of ore with cyanide solution followed by reduction with zinc.
0%
In Hall-Heroult process, the electrolyte used is a molten mixture of alumina, sodium hydroxide and cryolite.

Explanation

(a)

$Cr_{2}O_{3}+2Al\rightarrow Al_2O_3+2Cr^{3+}$

(b)

$2PbS+2PbO\rightarrow 2PbO+2SO_{2}$

$PbS+2PbO\rightarrow 3Pb+SO_{2}$ (self reduction)

$PbO+C\rightarrow Pb+CO$ (carbon reduction)

(c)

$ZnO+C\rightarrow Zn+CO$ (carbon reduction)

(d)

$4Au(S)+8CN(aq)+2H_{2}O(aq)+O_{2}(g)\rightarrow 4[Au(CN)_{2}]^{-} (aq)+4OH^{-}(aq)$ - leaching

$2[Au(CN]_{2}]^{-}(aq)+Zn(S)\rightarrow 2Au(S)+[Zn(CN)_{4}]^{2-}(aq)$ - reduction

(e) It is a molten mixture of alumina and cryolite

Given below are the steps for extraction of copper from its ore. The balance reaction involved in reduction of copper(I) oxide with copper(I) sulphide is given in the reaction below.

$2Cu_{2}O + Cu_{2}S \xrightarrow{Heat} 6Cu + SO_{2}$ .

This reaction is known as:

0%
auto-reduction
0%
catalytic- reduction
0%
acid reduction
0%
none of these

Which of the following reactions does not occur in Bessemer's converter?

0%
$2Cu_{2}S+5O_{2}\rightarrow 2CuSO_{4}+2CuO$
0%
$2Cu_{2}S+3O_{2}\rightarrow 2Cu_{2}O+2SO_{2}\uparrow$
0%
$2CuFeS_{2}+O_{2}\rightarrow Cu_{2}S+2FeS+SO$
0%
$FeO+SiO_2\rightarrow FeSiO_3$

Explanation

In the extraction of copper, following reactions occur in Bessemer converter:

$2Cu_{2}S+3O_{2}\rightarrow 2CuO+2SO_{2}$

$Cu_{2}S+2Cu_{2}O\rightarrow 6Cu+SO_{2}$

$2Cu_2S +5O_2 \rightarrow 2CuSO_4 + 2 CuO$

$2Cu_2S +Cu_2SO_4 \rightarrow 4Cu + 2 SO_2$

$FeO+SiO_2 \rightarrow FeSiO_3$

Roasting takes place in a furnace in the presence of a current of air. In this process,

$2CuFeS_{2}+O_{2}\rightarrow Cu_{2}S+2FeS+SO$ , reaction takes place.

CBSE Questions for Class 12 Engineering Chemistry General Principles And Processes Of Isolation Of Elements Quiz 2 - MCQExams.com

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Practice Class 12 Engineering Chemistry Quiz Questions and Answers

CBSE Questions for Class 12 Engineering Chemistry General Principles And Processes Of Isolation Of Elements Quiz 2 - MCQExams.com

0:0:2

Practice Class 12 Engineering Chemistry Quiz Questions and Answers

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