CBSE Questions for Class 12 Engineering Chemistry General Principles And Processes Of Isolation Of Elements Quiz 11 - MCQExams.com

Elements found in native state are
170479.png
  • Pb and Bi as they are in p-block
  • Hg and Os as they are in liquid state
  • C and Si as they are non-metals
  • Pt and Au as they are at the bottom of the electrochemical series
Froth flotation process which is used for the concentration of sulphide ore:
  • is based on the difference in wettability of different minerals
  • uses sodium ethyl xanthate, $$ C_2H_5OCS_2Na$$ as collector
  • uses NaCN as depresent in the mixture of ZnS and PbS when ZnS forms soluble complex and PbS forms froth
  • All of the above are correct
Select correct statement:
  • In the decomposition of an oxide, into oxygen and gaseous metal, entropy increases.
  • Decomposition of an oxide is an endothermic change.
  • To make $$\Delta G^{\circ}$$ negative, temperature should be high enough so that T $$\Delta S^{\circ}\, >\, \Delta H^{\circ}$$.
  • All of the above are correct statements.
The chemical process in the production of steel from haematite ore involves ___________.
  • reduction
  • oxidation
  • reduction followed by oxidation
  • oxidation followed by reduction

Find out B in the given process.
215698_4679cfe2a90d4596a634725f00148372.png
  • $$Na[Al(OH)_4]$$
  • $$NaOH$$
  • $$H_2SO_4$$
  • $$Al_2O_3$$
Carbon reduction process is not commercially applicable for which of the following set of oxides to extract the respective metal?

(I) $$ZnO$$  (II) $$Fe_2O_3$$   (III) $$Al_2O_3$$  (IV) $$SnO_2$$  (V) $$MgO$$
  • $$ZnO, Fe_2O_3, SnO_2$$
  • $$ZnO, SnO_2, MgO$$
  • $$MgO, Al_2O_3$$
  • $$MgO, SnO_2, Al_2O_3$$,

Find out A :
215696.jpg
  • $$CuFeS_2$$
  • $$MgCl_2.6H_2O$$
  • $$Al_2O_3.2H_2O$$
  • $$Fe_2O_3$$
Zn-Ag alloy formed in the upper layer of molten lead is skimmed off from the surface of the molten lead by perforated ladles. This alloy contains leed as impurity, This impurity of Pb is removed by :
  • distillation process
  • cupellation
  • liquation
  • Bett's electrolysis
Select the correct statements for Ellingharn diagram:
  • The slope of the curves of the formation of metal oxide is +ve because $$\Delta \mathring{G}$$ becomes less negative or increases with the rise in temperature
  • Each curve is a straight line except when some change takes place in phase $$(s\rightarrow l or l \rightarrow g)$$
  • Each curve is not a straight line except when some change takes place in phase $$(s\rightarrow l or l \rightarrow g)$$
  • The slope of the curves of the formation of metal oxide is -ve because $$\Delta \mathring{G}$$ becomes less negative or increases with the rise in temperature
Which of the following oxides cannot be reduced to metal by carbon?
  • $$ZnO$$
  • $$Al_2O_3$$
  • $$CuO$$
  • $$CaO$$
Carbon can be used to reduce the number of oxides and other compounds, and because of the low cost and availability of coke, this method is widely used. But the disadvantages are that:
  • high temperature is needed, which is expensive
  • many metals combine with carbon to form carbides
  • low temperature is needed, which is expensive
  • many metal combine with carbon and do not form carbides
Froth floatation process used for the concentration of sulphide ore:
  • is based on the difference in wettability of different minerals
  • uses sodium ethyl xanthate ($$C_2H_5OCS_2Na$$) as a collector
  • uses $$NaCN$$ as depressant in the mixture of $$ZnS$$ and $$PbS$$ when $$ZnS$$ forms soluble complex and $$PbS$$ forms froth
  • uses pine oil as frothing agent
Which of the following is incorrect on the basis of the above Ellingham diagram for carbon?
215212_7dc787b72cd0498da36c6b0ad84d6d88.png
  • Upto 710$$^{\circ}$$C, the reaction of forrnation of $$CO_2$$ is energetically more favorable, but above 710$$^{\circ}$$C, the formation of CO is preferred.
  • In principle, carbon can be used to reduce any metal oxide at a sufficiently high temperature.
  • $$\Delta S(C_{(s)} + 1/2 O_{2(g)} \longrightarrow CO_{(g)}) < \Delta S (C_{(S)} + O_{2(g)} \longrightarrow CO_{2(g)}$$
  • Carbon reduces many oxides at elevated temperature because $$\Delta G$$  vs temperature line has a negative slope.
Ag can be obtained from purified Zn-Ag alloy by :
  • distillation
  • poling
  • liquation
  • reduction
Find out F in the given flowchart.
215706_27f6047c42c949fd9fc8c59a08c1c155.png
  • cathode
  • anode
  • electrolyte
  • none of these
A metal oxide $$MO_{(s)}$$ can be reduced by carbon or carbon monoxide successfully when the line in Ellingham diagram for reaction (i):
215773_8973029eaf514e5fafa549e2b698e071.png
  • lies above the line for one of the reactions (ii) to (iv)
  • intersects the line for one of the reactions (ii) to (iv)
  • lies below the line for one of the reactions (ii) to (iv)
  • may lie above or below the line for one of the reactions (ii) to (iv) depending upon the temperature
CuO can be reduced to Cu conveniently by using C or CO at any temperature :
215773_8973029eaf514e5fafa549e2b698e071.png
  • approximately equal to room temperature
  • above room temperature
  • below room temperature
  • at all temperature

Find out E :
215696.jpg
  • $$Na_3GeF_6$$
  • $$Na_3AlF_6$$
  • $$Al_2O_3$$
  • none of these
These equilibria can be discussed in terms of thermodynamic functions.
For the reaction :

(i) $$\displaystyle M_{(s)} + \frac{1}{2} O_{2(g)} \rightarrow MO_(s)$$
(ii) $$\displaystyle \frac{1}{2} C_{(s)} + \frac{1}{2} O_{2(g)} \rightarrow \frac{1}{2} CO_{2(g)}$$
(iii) $$\displaystyle C_{(s)} + \frac{1}{2} O_{2(g)} \rightarrow CO_{(g)}$$
(iii) $$\displaystyle CO_{(g)} + \frac{1}{2} O_{2(g)} \rightarrow CO_{2(g)}$$

The temperature dependence of $$\Delta \mathring{G}$$ of reaction (i) to (iv) is shown in the given diagram. This is known as the Ellingham diagram. With the help of the Ellingham diagram, one can easily predict the most suitable reducing agent for the reduction of metal oxides.

$$AI_2O_3$$ can be reduced by carbon at a temperature of:

215773_8973029eaf514e5fafa549e2b698e071.png
  • $$30^{\circ}$$C
  • $$500^{\circ}$$C
  • $$2000^{\circ}$$C
  • $$> 2500^{\circ}$$C
In the context of the Hall - Heroult process for the extraction of Al, which of the following statements is false?
  • $$CO$$ and $$CO_2$$ are produced in this process
  • $$Al_2O_3$$ is mixed with $$CaF_2$$ which lowers the melting point of the mixture and brings conductivity
  • $$Al^{3+}$$ is reduced at the cathode to $$Al$$
  • $$Na_3AlF_6$$ serves as the electrolyte
All minerals are not the ore but all ores are minerals. The extraction of a particular metal depends upon several factors and overall it has to be convenient and economical.

Which of the following statement is true?
  • Na-ethyl xanthate is used as frother exclusively.
  • Levigation cannot be applied for sulphide in any condition.
  • Froth floatation can be applied for non-sulphide ore also using suitable activator.
  • Impurities like S and As are removed as elemental vapor in roasting.
Find out C in the given flowchart:
215701_881421d9c788437ead441d581b39080d.png
  • $$CO_2$$
  • $$SO_2$$
  • $$SO$$
  • $$NO_2$$
Which one of the following oxides is reduced by water gas to obtain the metal during its extraction?
  • $$NiO$$
  • $$ZnO$$
  • $$WO_{3}$$
  • $$Fe_{2}O_{3}$$
Which one of the following methods is used in the concentration of sulphide ore ?
  • Froth floation
  • Smelting
  • Roasting
  • Leaching
The principle behind froth floatation is:
  • preferential wetting of ore and gangue particles.
  • difference is specific gravity of ore and gangue particles.
  • magnetic properties of ore and gangue.
  • electrical properties of gangue particles.
Match items of Column I with the items of Column II and assign the correct code:

Column IColumn II
(a)Cyanide process(i)Ultrapure $$Ge$$
(b)Froth floatation process(ii)Dressing of $$ZnS$$
(c)Electrolytic reduction(iii)Extraction of $$Al$$
(d)Zone refining(iv)Extraction of $$Au$$
(v)Purification of $$Ni$$
  • a - (iv), b - (ii), c - (iii), d - (i)
  • a - (ii), b - (iii), c - (i), d - (v)
  • a - (i), b - (ii), c - (iii), d - (iv)
  • a - (iii), b - (iv), c - (v), d - (i)
The zone refining process of metals is based on the principle of :
  • excess noble character of the liquid metal than that of impurity
  • lower melting point of the impurity than that of pure metal
  • greater solubility of impure metal than that of impurity
  • greater solubility of the impurities in the molten state than in the solid
From the Ellingham graphs on carbon, which of the following statements is false?
572777_77319abd21434434afa4f34eb22bc727.png
  • $$CO_2$$ is more stable than $$CO$$ at less than $$983$$ K
  • $$CO$$ reduces $$Fe_2O_3$$ to $$Fe$$ at less than $$983$$ K
  • $$CO$$ is less stable than $$CO_2$$ at more than $$983$$ K
  • $$CO$$ reduces $$Fe_2O_3$$ to $$Fe$$ in the reduction zone of Blast furnace
$$\Delta G^o$$ versus $$ T $$ plot in the Ellingham's diagram slopes downward for which of the reaction?
  • $$C+\dfrac{1}{2}O_2\rightarrow CO$$
  • $$CO+\dfrac{1}{2}O_2\rightarrow CO_2$$
  • $$2Ag+\dfrac{1}{2}O_2\rightarrow Ag_2O$$
  • $$Mg+\dfrac{1}{2}O_2\rightarrow MgO$$
From the following identify the correct ones.
  • $$Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$$
  • $$ZnO + C \rightarrow Zn + CO$$
  • $$Ca_3(PO_4)_2 + C \rightarrow P$$
  • $$PbO + C \rightarrow Pb$$
The reducing agent in thermite process is:
  • $$Al$$
  • $$Mg$$
  • $$Fe$$
  • $$Si$$
The correct statements with respect to Ellingham's diagram among the following are
(I) Magnesium reduces aluminium oxide below 1700 K
(II) Aluminium reduces magnesium oxide above 1700 K
(III) Aluminium reduces magnesium oxide below 1700 K
(IV) Magnesium reduces aluminium oxide above 1700 K
  • I & II
  • II & III
  • III & IV
  • II, III & IV
The mass of carbon anode consumed (giving the only carbon dioxide) in the production of $$270kg$$ of aluminium metal from bauxite by the Hall process is: 
[atomic mass $$Al=27$$]
  • $$180\ kg$$
  • $$270\ kg$$
  • $$540\ kg$$
  • $$90\ kg$$
Copper, a metal known from ancient times, has many uses, some of which are mentioned here. Can you pick the false one?
  • As an alloy in high-speed drills
  • In brass utensils and bronze statues
  • In electric motor coils
  • In tapes and water connections
Pyrolusite is:
  • a sulphide ore of $$Mn$$
  • an oxide ore of $$Mn$$
  • a carbide ore of $$P$$
  • a chloride ore of $$Zn$$
Which of the following ores are concentrated by Froth Flotation.
  • Oxide ores
  • Chloride ores
  • Sulphide ores
  • Nitride ores
The reduction of an oxide by aluminium is called:
  • Kroll's process
  • Van Arkel process
  • Ellingham process
  • Goldschmidt's aluminothermite process
Electrolytic reduction of alumina to aluminium by Hall-Heroult process is carried out:
  • in the presence of $$NaCl$$
  • in the presence of Hnorite
  • 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
The mineral carnallite contains __(i)___and __(ii)____metals. ____(iii)____ is purified by cupellation and ____(iv)_____is purified by distillation.
  • (i) -calcium , (ii)- zinc, (iii)- mercury, (iv)- tin
  • (i)- calcium, (ii)- magnesium, (iii)- zinc, (iv)- lead
  • (i)- potassium, (ii)- calcium, (iii)- copper, (iv)- mercury
  • (i)- magnesium, (ii)-potassium, (iii)- silver, (iv)- mercury
Which of the following statements is correct according to the basic concept of thermodynamics which govern the feasibility of a metallurgical process?
  • When the value of $$\triangle $$G is positive for the equation $$\triangle $$G=$$\triangle $$H-T$$\triangle $$S, the reaction will proceed.
  • If reactants and products of two reactions are put together and net $$\triangle $$G is -ve, the overall reaction will occur.
  • On increasing the temperature, the value of $$\triangle $$G becomes +ve.
  • Feasibility of thermal oxidation of an ore can be established by Ellingham diagram in which a straight line shows the reduction reaction will proceed.
Which of the following statements is not correct?
  • Zinc can be extracted from its ore by roasting followed by extraction with coke.
  • In reverberatory furnace, both oxidation and reduction processes can be carried out.
  • Silver is purified by distillation or liquation process.
  • Highly pure metals are obtained by zone refining.
Match the column I with column II and mark the appropriate choice.
Column IColumn II
(A)Metals used as semiconductors(i)Aluminium
(B)Electrolytic reduction(ii)Zone refining
(C)Cyanide process(iii) Dressing of $$ZnS$$
(D)Froth floatation process(iv) Extraction of $$Ag$$
  • (A) $$\rightarrow$$(i), (B)$$\rightarrow$$(iii), (C)$$\rightarrow$$(ii), (D) $$\rightarrow$$ (iv)
  • (A) $$\rightarrow$$(iii), (B)$$\rightarrow$$(iv), (C)$$\rightarrow$$(ii), (D) $$\rightarrow$$ (i)
  • (A) $$\rightarrow$$(iv), (B)$$\rightarrow$$(ii), (C)$$\rightarrow$$(iii), (D) $$\rightarrow$$ (i)
  • (A) $$\rightarrow$$(ii), (B)$$\rightarrow$$(i), (C)$$\rightarrow$$(iv), (D) $$\rightarrow$$ (iii)
Below point 'A' FeO can_____.
935736_2eaf70f66f334f449ac90ddf1b180f6d.png
  • be reduced by carbon monoxide only
  • be reduced by both carbon monoxide and carbon
  • be reduced by carbon only
  • not be reduced by both carbon monoxide and carbon
In the following Ellingham diagram, X, Y and Z represent graphs for metal oxides. Select the correct option.
935696_2c1faf788bf1468e8aa5aaab6e19420b.png
  • Y will reduce oxide of Z.
  • Y will reduce oxide of X.
  • Z will reduce oxide of X.
  • Z will reduce oxide of Y.
For the reduction of FeO at the temperature corresponding to point D, which of the following statement is correct?
935737_6da1c58c974c456c9b01fa1491b44ff9.png
  • $$\triangle G^0$$ value for the overall reduction with carbon monoxide is zero.
  • $$\triangle G^0$$ value for the overall reaction with a mixture of 1 mol carbon and 1 mol oxygen is positive.
  • $$\triangle G^0$$ value for the overall reduction with a mixture of 2 mol carbon and 1 mol oxygen will be positive.
  • $$\triangle G^0$$ value for the reduction reaction with carbon monoxide is negative.
Which of the following is not correct observation based on Ellingham diagram?
  • A metal can reduce the oxide of other metal which lies above it in the Ellingham diagram.
  • $$CO$$ is more effective than $$C$$ as reducing agent below $$170^0C$$.
  • $$\Delta G^0$$ of metal oxide is higher than of $$CO_2$$ hence oxidation of metal sulphides to oxides is not favourable.
  • Need for conversion of metal sulphide to metal oxide before reduction can be explained thermodynamically.
Choose the correct option of temperature at which carbon reduces FeO to iron and produces CO.
935735_7e9cbcf118914339b33bf5a82743fb7f.png
  • Below temperature at point A
  • Approximately at the temperature corresponding to point A
  • Above temperature at point A but below temperature at point D
  • Above temperature at point A
Impurities of sulphur, silicon, and phosphorus can be removed from cast iron by adding:
  • carbon which reduces the impurities
  • water which dissolves the impurities
  • limestone which changes impurities into oxides and pass into slag
  • iron oxide which reacts with impurities by forming slag
Carbon cannot be used to produce magnesium by chemical reduction of $$MgO$$ because:
  • carbon is not a powerful reducing agent
  • magnesium reacts with carbon to form carbides
  • magnesium is less electropositive than carbon
  • carbon does not react with magnesium
In Hall Heroult's process, the main reagent is mixed with:
  • $${B}_{2}{H}_{6}$$
  • $${C}_{2}{H}_{6}$$
  • $${Na}_{3}Al{F}_{6}$$
  • $$Si{H}_{4}$$
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