Ores and Metallurgy MCQ Questions & Answers in Inorganic Chemistry | Chemistry
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21.
Which of the following metals cannot be obtained by electrolysis?
A
$$Cr$$
B
$$Na$$
C
$$Ca$$
D
$$Mg$$
Answer :
$$Cr$$
Active metals can be obtained by electrolysis.
22.
Before introducing $$FeO$$ in blast furnace , it is converted to $$F{e_2}{O_3}$$ by roasting so that
A
it may not be removed as slag with silica
B
it may not evaporate in the furnace
C
presence of it may increase the $$m.pt.$$ of charge
D
None of these
Answer :
it may not be removed as slag with silica
$$FeO$$ is capable forming slag with $$Si{O_2}$$
$$Si{O_2} + FeO \to FeSi{O_3}$$
23.
Cryolite and fluorspar are mixed with $$A{l_2}{O_3}$$ during electrolysis for extraction of aluminium to
A
increase the mass of the reaction mixture
B
get other products at anode like fluorine
C
lower the melting point and increase the conductivity of the electrolyte
D
reduce aluminium oxide by cryolite
Answer :
lower the melting point and increase the conductivity of the electrolyte
No explanation is given for this question. Let's discuss the answer together.
24.
Which of the oxide groups among the following cannot be reduced by carbon?
A
$$C{u_2}O,Sn{O_2}$$
B
$$CaO,{K_2}O$$
C
$$PbO,F{e_2}{O_4}$$
D
$$F{e_2}{O_3},ZnO$$
Answer :
$$CaO,{K_2}O$$
$$Ca$$ and $$K$$ are strong reducing agents, hence their oxides can not be reduced with carbon.
25.
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?
A
Metal sulphides are thermodynamically more stable than $$C{S_2}$$
B
$$C{O_2}$$ is thermodynamically more stable than $$C{S_2}$$
C
Metal sulphides are less stable than the corresponding oxides
D
$$C{O_2}$$ is more volatile than $$C{S_2}$$
Answer :
Metal sulphides are less stable than the corresponding oxides
NOTE : The reduction of metal sulphides by carbon reduction process is not spontaneous because $$\vartriangle G$$ for such a process is positive. The reduction of metal oxide by carbon reduction process is spontaneous as $$\vartriangle G$$ for such a process is negative. From this we find that on thermodynamic considerations $$C{O_2}$$ is more stable than $$C{S_2}$$ and the metal sulphides are more stable than corresponding oxides. In view of above the factor listed in choice (C) is incorrect and so is of no significance.
Hence the correct answer is (C)
26.
Blister copper obtained during extraction from cuprous oxide is called so because
A
it has blister like eruptions due to evolution of gas
B
it has a shining surface like blister
C
it is the most impure form of copper
D
its surface is uneven due to different thickness at different places
Answer :
it has blister like eruptions due to evolution of gas
Solidified copper obtained is called blister copper since it has blistered appearance due to the evolution of sulphur dioxide gas.
$$2C{u_2}O + C{u_2}S \to 6Cu + S{O_2}$$
27.
The significance of leaching in the extraction of aluminium is
A
it helps in removing the impurities like $$Si{O_2},F{e_2}{O_3}$$ etc from the bauxite ore
B
it converts the ore into oxide
C
it reduces melting point of the ore
D
it eliminates water from bauxite
Answer :
it helps in removing the impurities like $$Si{O_2},F{e_2}{O_3}$$ etc from the bauxite ore
No explanation is given for this question. Let's discuss the answer together.
28.
$$29.5\,mg$$ of an organic compound containing nitrogen was digested according to Kjeldahl’s method and the evolved ammonia was absorbed in $$20\,\,ml\,{\text{of}}\,0.1\,M\,HCl$$ solution. The excess of the acid required $$15\,\,mL\,{\text{of}}\,0.1\,\,M\,\,NaOH$$ solution for complete neutralization. The percentage of nitrogen in the compound is
29.
The substance used as froth stabilisers in frothfloatation process is
A
Potassium ethyl xanthate
B
Aniline
C
Sodium cyanide
D
Copper sulphate
Answer :
Aniline
Froth stabilizers cresols, aniline are added to stabilize the froth and enhance the nonwettability of the mineral particles.
30.
What is the process of leaching in case of low grade copper ores?
A
Leaching is carried out with $$NaOH$$ and $${O_2}.$$
B
Leaching is carried out with $$NaCN.$$
C
Leaching is carried out with acids in presence of $${H_2}.$$
D
Leaching is carried out by boiling the ore with water.
Answer :
Leaching is carried out with acids in presence of $${H_2}.$$
Leaching of low grade copper ores is carried out with acid or bacteria, when copper goes into solution as $$C{u^{2 + }}$$ ions.
$$Cu_{\left( {aq} \right)}^{2 + } + {H_{2\left( g \right)}} \to C{u_{\left( s \right)}} + 2H_{\left( {aq} \right)}^ + $$