Ores and Metallurgy MCQ Questions & Answers in Inorganic Chemistry | Chemistry
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201.
In a thermite process _________ is used as reducing agent.
A
$$Zn$$
B
$$Al$$
C
$$Mn$$
D
$$Fe$$
Answer :
$$Al$$
Thermite is a mixture of aluminium powder and ferric oxide. When this mixture is ignited, $$Al$$ reduces $$F{e_2}{O_3}$$ to $$Fe$$ while itself gets oxidized to $$A{l_2}{O_3}.$$
202.
Consider the following metallurgical processes :
(i) Heating impure metal $$CO$$ and distilling the resulting volatile carbonyl $$\left( {b.p.\,{{43}^ \circ }C} \right)$$ and finally decomposition at $${150^ \circ } - {200^ \circ }C$$ to get the pure metal
(ii) Heating the sulphide ore in air until a part is converted to oxide and then furher heating in the absence of air to let the oxide react with unchanged metal sulphide
(iii) Electrolysis of the molten electrolyte containing approximately equal amounts of
the metal chloride and $$NaCl$$ to obtained the metal
The processes used for obtaning magnesium, nickel and copper are respectively :
A
(i), (ii) and (iii)
B
(ii), (iii) and (i)
C
(iii), (i) and (ii)
D
(ii), (i) and (iii)
Answer :
(iii), (i) and (ii)
\[\begin{align}
& \left( \text{i} \right)\underset{\text{(impure)}}{\mathop{Ni}}\,+4CO\xrightarrow{{{50}^{\circ }}C}\left[ \underset{\text{(volite)}}{\mathop{Ni{{\left( CO \right)}_{4}}}}\, \right]\xrightarrow{{{230}^{\circ }}C}\underset{\text{(pure)}}{\mathop{Ni}}\,+4CO\uparrow \\
& \left( \text{ii} \right)C{{u}_{2}}S+\frac{3}{2}{{O}_{2}}\xrightarrow{\Delta }C{{u}_{2}}O+S{{O}_{2}} \\
& C{{u}_{2}}S+2C{{u}_{2}}O\xrightarrow[\text{temp}\text{.}]{\text{high}}6Cu+S{{O}_{2}} \\
& \left( \text{iii} \right)MgC{{l}_{2}}\left( s \right)\xrightarrow{\text{electrolysis}}M{{g}^{2+}}\left( l \right)+2C{{l}^{-}}\left( l \right) \\
& \text{At cathode :} \\
& M{{g}^{2+}}2{{e}^{-}}\to Mg\left( s \right) \\
& \text{At anode :} \\
& 2C{{l}^{-}}\left( l \right)\to C{{l}_{2}}\left( g \right)+2{{e}^{-}} \\
\end{align}\]
203.
Which of the following statements, about the advantage of roasting of sulphide ore before reduction is not true?
A
The $$\Delta G_f^ \circ $$ of the sulphide is greater than those for $$C{S_2}$$ and $${H_2}S.$$
B
The $$\Delta G_f^ \circ $$ is negative for roasting of sulphide ore to oxide.
C
Roasting of the sulphide to the oxide is thermodynamically feasible.
D
Carbon and hydrogen are suitable reducing agents for metal sulphides.
Answer :
Carbon and hydrogen are suitable reducing agents for metal sulphides.
The standard free energies of formation $$\left( {\Delta G_f^ \circ } \right)$$ of most of the sulphides are more negative than those of $$C{S_2}$$ and $${H_2}S.$$ Hence, neither carbon nor hydrogen can reduce metal sulphides to metal. The standard free energies of formation of oxides are much lower than those of $$S{O_2}.$$ Therefore, oxidation of metal sulphides to metal oxides is thermodynamically favourable. Hence sulphide ore is roasted to the oxide before reduction.
204.
When the sample of copper with zinc impurity is to be purified by electrolysis, the appropriate electrodes are
cathode
anode
(a)
pure zinc
pure copper
(b)
impure sample
pure copper
(c)
impure zinc
impure sample
(d)
pure copper
impure sample
A
(a)
B
(b)
C
(c)
D
(d)
Answer :
(d)
Pure metal always deposits at cathode.
205.
Which of the following is not an example of roasting?
A
$$2ZnS + 3{O_2} \to 2ZnO + 2S{O_2}$$
B
$$2PbS + 3{O_2} \to 2PbO + 2S{O_2}$$
C
$$2C{u_2}S + 3{O_2} \to 2C{u_2}O + 2S{O_2}$$
D
$$2C{u_2}O + C{u_2}S \to 6Cu + S{O_2}$$
Answer :
$$2C{u_2}O + C{u_2}S \to 6Cu + S{O_2}$$
It is an example of auto-reduction in which unoxidised copper sulphide reduces copper oxide.
206.
In the extraction of aluminium by Hall-Heroult process, purified $$A{l_2}{O_3}$$ is mixed with $$Ca{F_2}$$ to
(i) lower the melting point of $$A{l_2}{O_3}$$
(ii) increase the conductivity of molten mixture.
(iii) reduce $$A{l^{3 + }}$$ into $$Al\left( s \right).$$
(iv) acts as catalyst.
A
(i) and (ii)
B
(i), (ii) and (iii)
C
(iii) and (iv)
D
(ii), (iii) and (iv)
Answer :
(i) and (ii)
In the extraction of aluminium by Hall- Heroult process purified $$A{l_2}{O_3}$$ is mixed with $$Ca{F_2}$$ to lower the melting point by $$A{l_2}{O_3}$$ and increase the conductivity of molten mixture.
207.
Which of the following is not a carbonate ore?
A
Dolomite
B
Calamine
C
Siderite
D
Zincite
Answer :
Zincite
Zincite is $$ZnO.$$
208.
Which one of the following is a mineral of iron ?
In the extraction of copper from its sulphide ore, when ore is subjected to roasting, some of it is oxidised to $$C{u_2}O$$ which reacts with the remaining $${C{u_2}S}$$ ( sulphide ore ) to give copper metal.
$$2C{u_2}S + 3{O_2} \to 2C{u_2}O + 2S{O_2} \uparrow $$
$$2C{u_2}O + C{u_2}S \to 6Cu + S{O_2} \uparrow $$
In this process $$C{u_2}S$$ behaves as reducing agent.
210.
Match the column I with column II and mark the appropriate choice.
Column I
Column II
a.
Impure metal to volatile complex
1.
Blistered copper
b.
$$2C{u_2}O + C{u_2}S \to 6Cu + S{O_2}$$
2.
Mond process
c.
Purification of mercury
3.
Van Arkel process
d.
Purification of zirconium
4.
Liquation
A
a - 4, b - 3, c - 1, d - 2
B
a - 2, b - 1, c - 4, d - 3
C
a - 1, b - 2 , c - 4, d - 3
D
a - 3, b - 4, c - 1, d - 2
Answer :
a - 2, b - 1, c - 4, d - 3
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