Loading [MathJax]/jax/output/CommonHTML/jax.js

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 :
  • Cu2I2
  • CuI2
  • K2[CuI4]
  • 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
  • Fe2O3+CO2FeO+CO2
  • FeO+COFeO+CO2
  • Fe2O3+3C2Fe+3CO
  • CaO+SiO2CaSiO3
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
  • Na3AlF6
  • AlF3
  • 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 ΔGo negative, temperature should be high enough so that TΔSo>ΔHo
  • All are correct statements
Ellingham diagram represent : 
  • Change of ΔG with temperature
  • ΔH with temperature
  • ΔG with pressure
  • change of (ΔGTΔS-)
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 C2H5OCS2Na 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 Na2[Zn(CN)4] While PbS forms forth
  • PbS forms soluble complex Na2[Zn(CN)4] while ZnS forms forth
  • NaCN is never added in forth floatation process
correct statement in the electrolysis of Al2O3 by Hall-Heroult process is:
  • Cryolite Na3[AlF5] lowers the m.pt. of Al2O3 and increases its electrical conductivity
  • Al is obtained at cathode and CO2 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 Na2[Zn(CN)4]
  • PbS forms soluble complex Na2[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
  • H2S
  • Bi2S3
  • CS2
Which of the following elements can be prepared by heating the oxide above 400C
  • Hg
  • Mg
  • Fe
  • Al
Formation of which of the sulphides is most spontaneous?
  • HgS
  • Bi2S3
  • PbS
  • CS2
Free energy change of Hg and Mg for the conversion of oxides the slope of ΔG 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?
  • 1000C
  • 1500C
  • 500C
  • 1200C
At 1100C, which reaction is spontaneous to a maximum extent?
  • MgO+CMg+CO
  • ZnO+CZn+CO
  • MgO+ZnMg+ZnO
  • ZnO+MgMgO+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+CZn+CO
  • 1000C
  • >1100C
  • <500C
  • <1000C
Which of the following sulphides can not be reduced to metal by H2 at about 1000C ?
  • HgS
  • PbS
  • Bi2S3
  • All of these
Of the following reduction process, correct process are:
  • Fe2O3+CFe
  • ZnO+CZn
  • Ca3(PO4)2+CP
  • PbO+CPb
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                      Column II
(a) Sphalerite-                          (i) FeCO3
(b) Malachite-                          (ii) ZnCO3
(c) Calamine-                          (iii) Na3AlF6
(d) Cryolite-                             (iv) CuCO3.Cu(OH)2 
(e) Siderite                               (v) ZnS
  •  (a) (iii), (b) (i), (c) (v), (d) (ii), (e) (iv)
  •  (a) (v), (b) (iv), (c) (ii), (d) (i), (e) (iii)
  •  (a) (v), (b) (iii), (c) (ii), (d) (i), (e) (iv)
  •  (a) (v), (b) (iv), (c) (ii), (d) (iii), (e) (i)
  •  (a) (ii), (b) (iii), (c) (i), (d) (v), (e) (iv)
0:0:1


Answered Not Answered Not Visited Correct : 0 Incorrect : 0

Practice Class 12 Engineering Chemistry Quiz Questions and Answers