CBSE Questions for Class 12 Engineering Chemistry General Principles And Processes Of Isolation Of Elements Quiz 7 - MCQExams.com

A process employed for the concentration of sulphide ore is:
  • froth floatation
  • gravity separation
  • froth separation
  • gravity floatation
Gold does not occur in the combined form. It does not react with air or water. It is in the_______state.
  • native
  • combined
  • original
  • liquid
The process of leaching, alumina using sodium carbonate is called _________.
  • bayer's process
  • decomposition
  • cyanide process
  • hall's process
Which of the following is an oxide ore?
  • Malachite
  • Haematite
  • Chalcopyrite
  • Zinc blende
In chromite ore, the oxidation number of iron, and chromium are respectively.
  • +3, +2
  • +3, +6
  • +2, +6
  • +2, +3
$$NaCN$$ is sometimes added in the froth floatation process as a depressant when $$ZnS$$ and $$PbS$$ minerals are expected because:
  • $$ZnS$$ forms soluble complex $${ Na }_{ 2 }\left[ Zn{ \left( CN \right) }_{ 4 } \right] $$ while $$PbS$$ form froth
  • $$Pb{ \left( CN \right) }_{ 2 }$$ is precipitated while no effect on $$ZnS$$ form froth
  • $$PbS$$ forms soluble complex $${ Na }_{ 2 }\left[ Zn{ \left( Pb \right) }_{ 4 } \right] $$ while $$ZnS$$ form froth
  • $$NaCN$$ is never added in froth floatation process
Which of the following is the most common use of copper:
  • roofing
  • plumbing
  • electrical equipment
  • construction
Auto-reduction is employed in the metallurgy of :
  • $$Hg$$
  • $$Al$$
  • $$Ti$$
  • $$Zn$$
Thermal decomposition of ammonium dichromate gives:
  • $${ N }_{ 2 },{ H }_{ 2 }O$$ and $${ Cr }_{ 2 }{ O }_{ 3 }$$
  • $${ N }_{ 2 },N{ H }_{ 3 }$$ and $$CrO$$
  • $${ \left( N{ H }_{ 4 } \right) }_{ 2 }Cr{ O }_{ 4 }$$ and $${ H }_{ 2 }O$$
  • $${ N }_{ 2 },{ H }_{ 2 }O$$ and $$Cr{ O }_{ 3 }$$
  • $${ N }_{ 2 },{ H }_{ 2 }O$$ and $$CrO$$
Bessemer converter is used for the preparation of:
  • Steel
  • Wrought iron
  • Pig iron
  • Cast iron
 Which of the following metal is used with copper in the formation of alloy brass?
  • Zinc
  • Iron
  • carbon
  • silver
The purest zinc is made by.
  • Electrolytic refining
  • Zone refining
  • The van-Arkel method
  • Mond process
Which metallurgy involves leaching?
  • $$Au$$
  • $$Ag$$
  • Both (a) and (b)
  • None of these
Number of electrons involved in the electrodeposition of $$63.5\ g$$ of $$Cu$$ from a solution of $$CuSO_{4}$$ is?
  • $$6.022\times 10^{23}$$
  • $$3.011\times 10^{23}$$
  • $$12.044\times 10^{23}$$
  • $$6.022\times 10^{22}$$
The ore that is concentrated by froth floatation process is:
  • Cinnabar
  • Dawdle
  • Malachite
  • Zincite
Which method is used to get very pure germanium used in semiconductor ?
  • Vapour-phase refining
  • Electrolysis
  • Liquation
  • Zone-refining
Usually refractory metals are used in construction of furances because:
  • they are chemically inert
  • their melting point is high
  • they can withstand high temperature
  • none of the above
A solution is a homogeneous mixture of two or more substances. Which of the following is a solution?
  • Milk
  • Smoke
  • Brass
  • Face Cream
 Due to its high heat exchange rate, copper is used in:
  • dispenser
  • refrigerator
  • AC
  • all of them
The transition element used for making calorimeters is:
  • $$Cr$$
  • $$Ni$$
  • $$Zn$$
  • $$Cu$$
Among $$K, Mg, Au$$ and $$Cu$$, the one which is extracted by heating its ore in air is:
  • $$K$$
  • $$Mg$$
  • $$Au$$
  • $$Cu$$
Stainless steel contains:
  • $$Fe,Ni,Cr$$
  • $$Fe,Ni,Sn$$
  • $$Fe,C,S$$
  • $$Fe,P,Cr$$
Purification of aluminium by electrolytic refining is called:
  • Serpeck's process
  • Hoope's process
  • Hall's process
  • Baeyer's process
Considering Ellingham diagram, which of the following metals can be used to reduced alumina?
  • $$Mg$$
  • $$Fe$$
  • $$Cu$$
  • $$Zn$$
Bauxite, the ore of aluminium, is purified by which process?
  • Hoope's process
  • Hall's process
  • Mond's process
  • Liquation process
The ore that can be concentrated by magnetic separation method is:
  • bauxite $$(Al_{2}O_{3}.xH_{2}O)$$
  • pyrolusite $$(MnO_{2})$$
  • cuprite $$(Cu_{2}O)$$
  • zincite $$(ZnO)$$
The most common ore of iron is ___________.
  • calamine
  • hematite
  • zinc blende
  • copper pyrite
In the silver plating of copper, K[Ag$$(CN)_2$$] is used instead of Ag$$NO_3$$. The reason is:
  • a thin layer of Ag is formed om Cu
  • more voltage is required
  • $$Ag^+$$ ions are completely removed from solution
  • less availability of $$Ag^+$$ ions, as Cu cannot displace Ag from $$[Ag(CN)_2]^-$$ ion
Which of the following is the ore of $$Cu$$?
  • Ciderite
  • Magnetite
  • Calamine
  • Malachite
Which of the following factors is of no significance for roasting sulphide ores to the oxides and not subjecting the sulphide ores to carbon reduction directly?
  • Metal sulphides are thermodynamically more stable than $$CS_2$$
  • $$CO_2$$ is thermodynamically more stable than $$CS_2$$
  • Metal sulphides are less stable than the corresponding oxides
  • $$CO_2$$ is more volatile than $$CS_2$$
Which of the following is a non-metallic mineral?
  • Bauxite
  • Magnesium
  • Gypsum
  • Manganese
Identify the metal $$M$$ whose extraction is based on the following reactions:
$$MS+2{ O }_{ 2 }\longrightarrow M{ SO }_{ 4 }$$
$$2MS+3{ O }_{ 2 }\longrightarrow 2MO+2S{ O }_{ 2 }$$
$$MS+2MO\longrightarrow 3M+S{ O }_{ 2 }$$
$$MS+M{ SO }_{ 4 }\longrightarrow 2M+2S{ O }_{ 2 }\quad $$
  • magnesium
  • aluminium
  • lead
  • tin
Match the columns.
List IList II
A. Bauxite$$1.$$ Lead
B. Haematite$$2.$$ Thorium
C. Galena$$3.$$ Aluminium
D. Monazite$$4.$$ Iron
  • $$A - 3, B - 1, C - 4, D - 2$$
  • $$A - 4, B - 2, C - 1, D - 3$$
  • $$A - 3, B - 4, C - 1, D - 2$$
  • $$A - 2, B - 4, C - 3, D - 1$$
Which of the following statements is correct about the role of collectors added during forth floatation process?
  • Collectors enhance the non-wettability of ore particles
  • Collectors enhance the wettability of gangue particles
  • Collectors help in separating two sulphide ores present in the mixture
  • Collectors help ore particles to settle down below the froth
An excess of molybdenum in grassy areas results in poor growth of animals because it blocks the utilization of:
  • oxygen
  • iron
  • copper
  • selenium
Which of the following is a halide ore?
  • Cassiterite
  • Anglesite
  • Siderite
  • Carnallite
Sulphide ore of zinc/copper is concentrated by:
  • forth floatation
  • electromagnetic process
  • gravity process
  • distillation
An ore of tin containing, $$FeCrO_4$$ is concentrated by:
  • gravity separation
  • magnetic separation
  • forth floatation
  • leaching
Forth 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 ganaue and ore particles in frothing agent and water
  • difference in reactivity of gangue and ore particles with water and frothing agent.
Gold paint is made from:
  • copper
  • platinum
  • gold
  • antimony
Lithopone is a mixture of zinc sulphide and barium sulphate. It is used as a paint instead of white lead, because it:
  • does not become black in air
  • is more white
  • is more bright
  • does not become yellow in air
For which of the following ores forth floatation method is used for concentration?
  • Haematite
  • Zinc blende
  • Magnetite
  • Carnallite
Study the Ellingham diagram for the formation of some oxides and answer the following question.
At the point of intersection of $$Al_2O_3$$ and $$MgO$$ curves (A), $$\triangle G^0$$ becomes zero for the reaction,

     $$\frac{2}{3}Al_2O_3+2Mg \rightarrow + \frac{4}{3} Al$$

Below this point, magnesium can reduce alumina. Although thermodynamically feasible, Al is not used for reduction of $$MgO$$ because:
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  • temperature required is very high
  • the yields of metal is very low
  • the value of $$\triangle G^0$$ becomes positive
  • magnesium is not used as reducing agent for any reaction
Which of the following is not a method of refining of metals?
  • Electrolysis
  • Smelting
  • Poling
  • Liquation
From the Ellingham graph between Gibb's energy and temperature, out of $$C$$ and $$CO$$ which is a better reducing agent for $$ZnO$$?
  • Carbon
  • $$CO$$
  • Both of these
  • None of these
During the formation of the slag by the reaction of flux and impurities which of the following is an example of acidic and basic flux?
(i) $$FeO + SiO_2\rightarrow FeSiO_3$$
(ii) $$SiO_2+MgO\rightarrow MgO\rightarrow MgSiO_3$$
  • (i) $$SiO_2$$ - Acidic flux (ii) $$MgO$$ - Basic flux
  • (i) $$SiO_2$$ - Basic flux (ii) $$MgO$$ - Acidic flux
  • (i) $$SiO_2$$ - Basic flux (ii) $$MgO$$ - Basic flux
  • (i)$$ SiO_2$$ - Acidic flux (ii) $$MgO$$ - Acidic flux
The reaction $$Cr_2O_3+2Al\rightarrow Al_2O_3+2Cr(\triangle G^0 = -421 kJ) $$ is thermodynamically feasible due to -ve value of $$\triangle G.$$ Why does this reaction not take place at room temperature?
  • Certain amount of activation energy is essential for thermodynamically feasible reactions also.
  • Due to high melting point of chromium oxide the reaction does not take place.
  • Overall value of $$\triangle G$$ for the net reaction becomes positive.
  • Molecules of $$Cr_2O_3$$ and Al are not oriented properly.
Sulphides ores are converted to oxides before reduction. This is explained on the basis of which of the following?
  • Sulphides cannot be reduced easily while oxides can be reduced easily.
  • Sulphides decompose on reduction hence they are fixed converted to oxides.
  • Sulphide ores have higher melting points than oxides.
  • Oxides are more stable than sulphides hence easy to reduce.
Fill in the blanks with the correct choice.
The undesired impurities present in the ores are called ___(i)___. To remove the volatile impurities from the ore, the ___(ii)___ process is carried out. Flux combines with non-fusible impurities to form ___(iii)___. $$CaO$$ acts as a ___(iv)___ flux.
  • (i) - gangue, (ii) -roasting, (iii) - slag, (iv) -acidic
  • (i) - gangue, (ii) - calcination, (iii) - slag, (iv) - basic
  • (i) - anode mud, (ii) - leaching, (iii) - matrix, (iv) -acidic
  • (i) - gangue, (ii) -roasting, (iii) - solution, (iv) -acidic
Extraction of chlorine from brine is based on:
  • reduction
  • displacement
  • oxidation
  • evaporation
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