CBSE Questions for Class 12 Engineering Chemistry General Principles And Processes Of Isolation Of Elements Quiz 5 - MCQExams.com

The ore that is concentrated by froth floatation process is ___________.
  • cinnabar
  • bauxite
  • malachite
  • zineite
Zone-refining has been employed for preparing ultra-pure samples of:
  • Cu
  • Zn
  • Ge
  • Ag
Select the correct statement(s) :
  • When temperature is reised, a point will be reached where the graph crosses the $$\Delta$$G = 0 line. Below this temperature, the free energy of formatin of the oxide is negative, so the oxide is stable
  • When temperature is raised, a point will be reached where the graph crosses the $$\Delta$$G = 0 line. Above this temperature, the free energy of formation of the oxide is positive, and the oxide becomes unstable, and should decompose into the metal and dioxygen.
  • Theoretically, all oxides can be decomposed to give the metal and dioxygen if.a sufficiently high temperature can be attained.
  • Theoretically, all oxides cannot be decomposed to give the metal and dioxygen if a sufficiently high temperature can he attaincd
In which of the following isolations is no reducing agent required?
  • Iron from haematire
  • Tin from tin oxide
  • Mercury from cinnabar
  • Zine from zinc blende
Which of the following metal is sometimes found native in nature?
  • Aluminium
  • Copper
  • Sodium
  • Magnesium
Lead obtained from galena ore (PbS) by air reduction or carbon reduction process contains base metal (Cu, Bi, As, Sn, Zn) as impurities. Gelatin acts as an addition agent in the electrolysis of Pb. In the presence of gelatin, Pb becomes :
  • hard and brittle
  • soft and rubbery
  • smooth and uniform
  • only brittle
When $$FeCr_2O_4$$ (chromite) is reduced with $$Al$$:
  • $$Cr$$ and $$Fe_2O_3$$, are formed
  • $$Fe$$ and $$Cr_2O_3$$ are formed
  • $$Fe$$ and $$Cr$$ (ferrochrome) are formed
  • $$FeCrO_4$$. is formed
Select the correct statements for Ellingham diagram.
  • Any metal will reduce the oxide of other metals which lie above it in the Ellingham diagram
  • According to the Ellingham diagram, Al will not reduce MgO at temperature below 1350$$^{\circ}$$C
  • According to the Ellingham diagram, Al will reduce MgO at temperature below 1350$$^{\circ}$$C
  • Any metal will not reduce the oxide of other metals which lie above it in the Ellingham diagram
$$H_2$$ is not widely used as the reducing agent in metallurgic process because :
  • many metals react with $$H_2$$ at elevated temperature forming hydrides
  • there is a risk of explosion from $$H_2$$ and $$O_2$$ present in the air
  • reducing power of $$H_2$$ does not increase with temperature
  • reducing power of $$H_2$$, increases with temperature
Which of the following statement(s) is/are correct"?
  • The chemical processes in the production of steel from haematite ore involve reduction followed by

    oxidation.
  • In Hall-Heroult process, the electrolyte used is a molten mixture of alumina and cryolite or fluorspar.
  • Lead is extracted from its chief ore galena by both carbon reduction as well as self reduction,
  • Haematitic, cassiterite, and argentite are oxide ores.
The metal oxide which cannot be reduced to metal by carbon is _________.
  • $$ZnO$$
  • $$Fe_2O_3$$
  • $$PbO$$
  • $$Al_2O_3$$

Which of the given metal oxides is having minimum thermal decomposition temperature?
215734_8d89cc014aeb4687b1cf43915a933034.png
  • CaO
  • FeO
  • PbO
  • MgO
Electrolytic reduction of alumina to aluminium by Hall-Heroult process is carried out _______________.
  • in the presence of NaCl
  • in the presence of fluorite
  • in the presence of cryolite which forms a melt with lower melting temperature
  • in the presence of cryolite which forms a melt with higher melting temperature
Which of the following metal's oxide can be reduced by Fe as reducing agent at temperature $$T_1$$?
215735_371a032776ce4f2aa0c06230d30bbc98.png
  • Pb
  • Ca
  • Mg
  • None of these
Which one of the above oxidation curve is wrongly presented in the given Gibbs free energy vs temperature graph ?
215732_33b99f7f37ea4740b75c49c24fb8a85e.png
  • $$C \rightarrow CO_2$$
  • $$Ti \rightarrow TiO_2$$
  • $$Pb \rightarrow PbO$$
  • $$Mg \rightarrow MgO$$
Aquaregia is ___ part conc. HCI and ___ part conc. $$HNO_3$$.
  • one,three
  • one,one
  • three,three
  • three,one
(i) Metals can be recovered from their ores by chemical methods.

(ii) High purity metals can be obtained by zone refining method.

Which one is true /false.
  • (i) is true and (ii) is false
  • (ii) is true and (i) is false
  • (i) and (ii) are true
  • (i) and (ii) are false
Pb is a very important element of carbon family. It forms a number of compounds which are very useful in industries. The process of removal of base metals (Cu, Sn, Bi, As) from lead is called:
  • softening process
  • liquation
  • parke's process
  • cupellalion
The better reducing agent at $$7100^oC$$ is:
  • $$CO$$ (Ellingham diagram)
  • Coke
  • Both are equal
  • None of these
NaCN used in the froth flotation method for the purification of ore is:- 
  • $$ZnS$$ which contain $$PbS$$
  • $${Cu_2 S}$$ which contain $${Fe_2 S_3}$$
  • $$PbS$$ which contain $$ZnS$$
  • $$PbS$$ which contain $${SiO_2}$$
Which is wrongly mached:
  • Gun metal- $$\displaystyle Cu+Zn+Sn$$
  • Duralumin $$\displaystyle Cu+Al+Mn$$
  • German silver $$\displaystyle Cu+Zn+Ni$$
  • Electron $$\displaystyle Pb+Sn$$
Froth floatation process is used to concentrate magnetic ores.
  • True
  • False
Composition of azurite mineral is:
  • $$CuCO_3.CuO$$
  • $$Cu(HCO_3)_2.Cu(OH)_2$$
  • $$2CuCO_3.Cu(OH)_2$$
  • None of these
Predict the mode of occurrence of the following metals:
The correct answer is:
  • $$Na \rightarrow $$ combined form
  • $$Fe \rightarrow $$ combined form
  • $$Au \rightarrow $$ combined form
  • none of these
Volatile metals are purified by :
  • oxidation
  • distillation
  • liquation
  • electrolytic refining
Which one of the following metals can not be extracted by using Al as a reducing agent ________________.
  • $$\displaystyle Na$$ from $$\displaystyle { Na }_{ 2 }O$$
  • $$\displaystyle Cr$$ from $$\displaystyle { Cr }_{ 2 }{ O }_{ 3 }$$
  • $$\displaystyle Mn$$ from $$\displaystyle { MnO }_{ 2 }$$
  • $$\displaystyle Fe$$ from $$\displaystyle { Fe }_{ 2 }{ O }_{ 3 }$$
Identify the process to which the following reaction belongs : 

$$\displaystyle { Al }_{ 2 }{ O }_{ 3 }.{ 2H }_{ 2 }O+{ Na }_{ 2 }{ CO }_{ 3 }\longrightarrow { 2NaAlO }_{ 2 }+{ 2H }_{ 2 }O+{ CO }_{ 2 }$$

$$\displaystyle { 2NaAlO }_{ 2 }+{ 2H }_{ 2 }O+{ CO }_{ 2 } \underrightarrow { 50-{ 60 }^{ o }C } { Al }_{ 2 }{ O }_{ 3 }.{ 2H }_{ 2 }O+{ Na }_{ 2 }{ CO }_{ 3 }$$
  • Hall's process
  • Baeyer's process
  • Serpeck's process
  • None of these
Silver is purified by the distillation process.
  • True
  • False
Metals can be recovered from their ores by chemical methods.
  • True
  • False
Silver is found in nature both in native and combined state.  
  • True
  • False
Sulphide ore of copper can be concentrated by froth floatation process.
  • True
  • False
Which of the following metal is present in native state?
  • platinum
  • iron
  • potassium
  • copper
The most abundant metal in the earth crust is:
  • Copper
  • Silver
  • Aluminium
  • Silicon
Which of the following is not a property of aluminium?
  • Good conductor of heat and electricity
  • It is malleable
  • It is heavy
  • It is ductile
Silk moth feed on:
  • eucalyptus leaf
  • grapes Leaves
  • mulberry Leaves
  • neem leaves
Zone refining process is used for the:
  • Concentration of an ore
  • Reduction of a metal oxide
  • Purification of metal
  • Purification of an ore
Sulfide ores are usually dressed by the _____ process.
  • sieve process
  • froth floatation
  • magnetic floatation
  • none of these
Which of the following chemical reaction correctly shows Aqua-regia dissolving in gold?
  • $$Au+2[Cl]\longrightarrow AuCl_2\overset{HCl}{\longrightarrow} H_2[AuCl_4]$$
  • $$Ag+3[Cl]\longrightarrow AgCl_3\overset{HCl}{\longrightarrow} H[AgCl_4]$$
  • $$Au+3[Cl]\longrightarrow AuCl_3\overset{HCl}{\longrightarrow} H[AuCl_4]$$
  • $$Ag+2[Cl]\longrightarrow AgCl_2\overset{HCl}{\longrightarrow} H_2[AgCl_4]$$
During concentration of _____ ores by froth floatation process potassium ethyl xanthate is added.
  • sulphide
  • carbonate
  • halide
  • amide
The oil used in the froth floatation method for the purification of ore is _________.
  • Coconut oil
  • Olive oil
  • Pine oil
  • Castor oil
Which oil is used as frother in froth floatation process?
  • Mustard oil
  • Coconut oil
  • Olive oil
  • Pine oil

The diagram shows the sketch of an electrolytic cell used in the extraction of aluminium. At which electrode (A or B) is the aluminium formed?
285905_beb8e2c67586428e86e805d8e0adf4e9.png
  • A (Cathode)
  • B (Anode)
  • At both A and B
  • Cannot be determined

The diagram shows the sketch of an electrolytic cell used in the extraction of aluminium. What are the two aluminium compounds present in the electrolyte C?
285910_0f40cca31cda4909a1343c8dac86240d.png
  • Pure alumina (Al$$_2$$O$$_3$$) and cryolite (Na$$_3$$AlF$$_6$$)
  • Duralumin, magnalium
  • Cryolite, duralumin
  • none of the above
The substance added in water in the froth floatation process is
  • Olive oil
  • Pine oil
  • Coconut oil
  • None of the above
Silicon is the main constituent of _______.
  • alloys
  • rocks
  • animals
  • vegetables
$$\displaystyle Fe_{2}O_{3\left ( s \right )}+2Al_{\left ( s \right )}\rightarrow 2Fe_{\left ( l \right )}+Al_{2}O_{3\left ( s \right )}$$
The above reaction is known as _________ and it is highly ________ .
  • electrolysis, endothermic
  • refining, endothermic
  • calcination, exothermic
  • thermite reaction, exothermic

The diagram shows the sketch of an electrolytic cell used in the extraction of aluminium. What is the substance of which the electrodes A and B are made?
285899_232db5b0a4e04a88a0bfbcb000cf3591.png
  • Carbon and graphite
  • Zinc and copper
  • Copper and iron
  • None of the above
In the alumino thermic process, aluminium acts as:
  • an oxidizing agent
  • a flux
  • a reducing agent
  • a solder
Which of the following methods is used in purification of mercury?
  • Liquation
  • Distillation
  • Electrolytic refining
  • Chemical reduction
Liquation method is used for the purification of which of the following metals?
  • Tin
  • Lead
  • Bismuth
  • All of these
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