CBSE Questions for Class 12 Engineering Chemistry General Principles And Processes Of Isolation Of Elements Quiz 13 - MCQExams.com

Froth floatation process is used for the concentration of
  • oxide ores
  • sulphide ores
  • chloride ores
  • amalgams
Froth - floatation method is successful in separating impurities from ores because
  • the pure ore is lighter than water containing additives like pine oil , cresylic acid etc.
  • the pure ore is soluble in water containing additives like pine oil , cresylic acid etc.
  • the impurities are soluble in water containing additives like pine oil , cresylic acid etc.
  • the pure ore is not as easily wetted by water as by pine oil , cresylic acid etc.
Aluminium is used:
  • in thermite welding
  • as an oxidiser in metallurgy
  • for making untensils
  • in silvery paints
The white precipitate (P) is of :
  • $$Cu_{2}I_{2}$$
  • $$CuI_{2}$$
  • $$K_{2}\left [ CuI_{4} \right ]$$
  • None
A layer of coke is spread over bauxite during electrolytic reduction of alumina by Hall Heroult process. This layer acts as a/an
  • flux
  • slag to remove impurities
  • reducing agent
  • insulation and does not allow heat to escape
The reactions which does/do not occur in the reduction zone in the extraction of iron from haematite  ore is
  • $$ Fe_{2}O_{3}+CO\rightarrow 2FeO + CO_{2} $$
  • $$ FeO+CO\rightarrow FeO + CO_{2} $$
  • $$ Fe_{2}O_{3}+3C\rightarrow 2Fe+3CO $$
  • $$ CaO+SiO_{2}\rightarrow CaSiO_{3} $$
Which one of the following statements is incorrect? 
  • In Hall-Heroult process, the electrolyte used is molten mixture of alumina, sodium hydroxide and cryolite.
  • Lead is extracted from is chief ore by both carbon reduction and self reduction
  • Zinc is extracted from its chief ore by carbon reduction
  • Extraction of gold involves the leaching of ore with cyanide solution followed by reduction with zinc.
In the metallurgical extraction of zinc from $$ZnO$$, the reducing agent used is
  • Carbon monoxide
  • Sulphur dioxide
  • Carbon dioxide
  • Nitric oxide
The impurities associated with minerals used in metallurgy are collectively called
  • Slag
  • Flux
  • Gangue
  • Ore
The substance used in the thermite process of reducing metal ores is
  • Aluminium
  • Thorium
  • Heated platinum gauze
  • Carbon
When a metal is to be extracted from its ore if the gangue associated with the ore is silica , then
  • An acidic flux is needed
  • A basic flux is needed
  • Both acidic and basic flux are needed
  • Neither of them is needed
Thermite process is used to extract metals
  • when their oxides can't be reduced by carbon
  • when their carbonates do not yield oxides by thermal decomposition
  • when their sulphides can't be converted into oxides by roasting
  • when their melting points are very high
Which one of the following metals is extracted by thermal reduction process ?
  • Copper
  • Iron
  • Aluminium
  • Magnesium
Carbon reduction process is used for the extraction of
  • $$Hg$$
  • $$Zn$$
  • $$Cr$$
  • $$Fe$$
In Hall's process the main reagent is mixed with
  • $$NaF$$
  • $$Na_{3}AlF_{6}$$
  • $$AlF_{3}$$
  • None of these
Heating with carbon in absence of air is known as
  • Reduction
  • Carbon - reduction
  • Smelting
  • Roasting
Zone refining is a technique used primarily for which one of the following process
  • Alloying
  • Tempering
  • Sintering
  • Purification
The chemical processes in the production of steel from haematite ore involve
  • reduction
  • oxidation
  • reduction followed by oxidation
  • oxidation followed by reduction
The extraction of nickel involves 
  • the formation of $$ Ni(CO)_4 $$
  • the decomposition of $$ Ni(CO)_4 $$
  • the formation and thermal decomposition of $$ Ni(CO)_4 $$
  • the formation and catalytic decomposition of $$ Ni(CO)_4 $$
While extracting an element from its ore, the ore is ground and leached with dilute KCN solution to form the soluble product potassium argentocyanide. The element is
  • Lead
  • Chromium
  • Manganese
  • Silver
In the electrolytic purification of copper some gold is found in the
  • cathode
  • cathode mud
  • anode mud
  • electrolyte
Select correct statement:
  • The decomposition of an oxide into oxygen and metal vapour increases
  • Decomposition of an oxide is an endothermic change
  • To make $$\Delta G^{o}$$ negative, temperature should be high enough so that $$T \Delta S^{o} > \Delta H^{o}$$
  • All are correct statements
Ellingham diagram represent : 
  • Change of $$ \Delta G $$ with temperature
  • $$ \Delta H $$ with temperature
  • $$ \Delta G $$ with pressure
  • change of ($$ \Delta G - T \Delta S $$-)
Copper metal is used in :
  • Making electric wires
  • Filing tooth cavities
  • Making fuse wires
  • Preparation of hydrogen
In the alumino-thermite process, Al acts as:
  • an oxidizing agent
  • a flux
  • solder
  • a reduction agent
Aluminium is not used to make
  • Foils
  • Wires
  • Fireworks
  • Utensils
Forth floatation process used for the concentration of sulphide ore:
  • Is based on the difference in wettability of different minerals
  • uses sodium ethyl xanthate $$C_{2}H_{5}OCS_{2}Na$$ as collector
  • uses NaCN as depressant in the mixture of ZnS forms soluble complex and Pbs forms forth
  • All are correct statements
Which of the following pair is incorrectly matched ?
  • van Arkel method - Zirconium
  • Kroll's process - Titanium
  • Froth floatation - Cerussite
  • Distillation - Zinc
NaCN is sometimes added in the forth flotation process as depressant when ZnS and PbS minerals are expected because:
  • $$Pb (CN)_{2}$$ is precipitated while no effect on ZnS
  • Zns forms soluble complex $$Na_{2}[Zn(CN)_{4}]$$ While PbS forms forth
  • PbS forms soluble complex $$Na_{2}[Zn(CN)_{4}]$$ while ZnS forms forth
  • NaCN is never added in forth floatation process
correct statement in the electrolysis of $$Al_{2}O_{3}$$ by Hall-Heroult process is:
  • Cryolite $$Na_{3}[AlF_{5}]$$ lowers the m.pt. of $$Al_{2}O_{3}$$ and increases its electrical conductivity
  • Al is obtained at cathode and $$CO_{2}$$ at anode
  • both (a) and (b) are correct
  • none of the above
When ZnS and PbS minerals are present together, then NaCN is added to separaye them in the forth floaatation process as a depressant, because:
  • $$Pb (CN)_{2}$$ is precipitated while no effect on ZnS
  • ZnS forms soluble complex $$Na_{2}[Zn(CN)_{4}]$$
  • PbS forms soluble complex $$Na_{2}[Zn(CN)_{4}]$$
  • The cannot be separated by adding NaCN
Which of the following substance acts as collector in froth floatation method?
  • Sodium xenate
  • Sodium pyrophosphate
  • Sodium nitroprusside
  • Sodium ethyl xanthate
High purity copper metal is obtained by :
  • carbon reduction
  • hydrogen reduction
  • electrolytic reduction
  • thermite reduction
Which sulphide occurs to minimum extent in nature 
  • $$HgS$$
  • $$H_{2}S$$
  • $$Bi_{2}S_{3}$$
  • $$CS_{2}$$
Which of the following elements can be prepared by heating the oxide above $$400^{\circ}C$$ ? 
  • Hg
  • Mg
  • Fe
  • Al
Formation of which of the sulphides is most spontaneous?
  • HgS
  • Bi$$_{2}$$S$$_{3}$$
  • PbS
  • CS$$_{2}$$
Free energy change of Hg and Mg for the conversion of oxides the slope of $$\Delta G$$ vs. T has been changed above the boiling point of the given metal because : 
  • above the boiling point of the given metal the entropy is increased
  • above the boiling point of the metal the entropy is decreased
  • above the boiling point of the metal the entropy change is equal to zero
  • All of these
At what temperature, zinc and carbon  have equal affinity for oxygen?
  • $$1000^{\circ}C$$
  • $$1500^{\circ}C$$
  • $$500^{\circ}C$$
  • $$1200^{\circ}C$$
At $$1100^{\circ}C$$, which reaction is spontaneous to a maximum extent?
  • $$MgO+C\rightarrow Mg+CO$$
  • $$ZnO + C \rightarrow Zn +CO$$
  • $$ MgO+Zn\rightarrow Mg + ZnO $$
  • $$ZnO + Mg \rightarrow MgO + Zn $$
In the electrolytic refining of copper, Ag and Au are found :
  • on anode
  • in electrolyte solution
  • in anode mud
  • in cathode mud
To make the following reduction process spontaneous, temperature should be : $$ZnO+C\rightarrow Zn+CO$$
  • $$1000^{\circ}C$$
  • $$>1100^{\circ}C$$
  • $$<500^{\circ}C$$
  • $$<1000^{\circ}C$$
Which of the following sulphides can not be reduced to metal by $$H_{2}$$ at about $$1000^{\circ}C$$ ?
  • $$HgS$$
  • $$PbS$$
  • $$Bi_{2}S_{3}$$
  • All of these
Of the following reduction process, correct process are:
  • $$Fe_{2}O_{3}+C\rightarrow Fe$$
  • $$ZnO + C \rightarrow Zn $$
  • $$Ca_{3}(PO_{4})_{2}+C\rightarrow P$$
  • $$PbO + C \rightarrow Pb$$
Elements found in the combined state are often present as oxides, carbonates, sulphides and silicates.
  • True
  • False
Froth floatation process of concentration is based on the
  • preferential wetting properties with the frothing agent and water
  • difference in the specific gravities of gangue and ore particles
  • difference in solubility of gangue and ore particles in frothing agent and water
  • difference in reactivity of gangue and ore particles with water and frothing agent.
Which one of the following ores is best concentration by forth-flotation method?
  • Malachite
  • Cassiterite
  • Galena
  • Magnetite
Which of the following is most economically refined by fractional distillation?
  • $$Zn$$
  • $$Ni$$
  • $$Cu$$
  • $$Fe$$
Match the following
Column I $$\quad$$                     Column II
(a) Sphalerite-                          (i) $$\mathrm{FeCO}_{3}$$
(b) Malachite-                          (ii) $$\mathrm{ZnCO}_{3}$$
(c) Calamine-                          (iii) $$\mathrm{Na}_{3} \mathrm{AlF}_{6}$$
(d) Cryolite-                             (iv) $$CuCO_{3}.Cu(OH)_{2}$$ 
(e) Siderite                               (v) $$\mathrm{ZnS}$$
  • $$\begin{array}{lllll}\text { (a) }-(\mathrm{iii}), & \text { (b) }-(\mathrm{i}), & \text { (c) }-(\mathrm{v}), & \text { (d) }-(\mathrm{ii}), & \text { (e) }-(\mathrm{iv})\end{array}$$
  • $$\begin{array}{lllll}\text { (a) }-(\mathrm{v}), & \text { (b) }-(\mathrm{iv}), & \text { (c) }-(\mathrm{ii}), & \text { (d) }-(\mathrm{i}), & \text { (e) }-(\mathrm{iii})\end{array}$$
  • $$\begin{array}{lllll}\text { (a) }-(\mathrm{v}), & \text { (b) }-(\mathrm{iii}), & \text { (c) }-(\mathrm{ii}), & \text { (d) }-(\mathrm{i}), & \text { (e) }-(\mathrm{iv})\end{array}$$
  • $$\begin{array}{lllll}\text { (a) }-(\mathrm{v}), & \text { (b) }-(\mathrm{iv}), & \text { (c) }-(\mathrm{ii}), & \text { (d) }-(\mathrm{iii}), & \text { (e) }-(\mathrm{i})\end{array}$$
  • $$\begin{array}{lllll}\text { (a) }-(\mathrm{ii}), & \text { (b) }-(\mathrm{iii}), & \text { (c) }-(\mathrm{i}), & \text { (d) }-(\mathrm{v}), & \text { (e) }-(\mathrm{iv})\end{array}$$
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