Ores and Metallurgy MCQ Questions & Answers in Inorganic Chemistry | Chemistry
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181.
Among the following statements the incorrect one is
A
Calamine and siderite are carbonates
B
Argentite and cuprite are oxides
C
Zinc blende and iron pyrites are sulphides
D
Malachite and azurite are ores of copper.
Answer :
Argentite and cuprite are oxides
Cuprite is $$C{u_2}O$$ and Argentite is $$A{g_2}S.$$
182.
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 reduction of metal sulphides.
Answer :
Carbon and hydrogen are suitable reducing agents for reduction of metal sulphides.
The sulphide ore is roasted to oxide before reduction because the $$\Delta G_f^ \circ $$ of most of the sulphides are greater than those of $$C{S_2}$$ and $${H_2}S,$$ therefore neither $$C$$ nor $$H$$ can reduce metal sulphide to metal. Further, the standard free energies of formation of oxide are much less than those of $$S{O_2}.$$ Hence oxidation of metal sulphides to metal oxide is thermodynamically favourable.
183.
Which of the following is a halide ore?
A
Cassiterite
B
Anglesite
C
Siderite
D
Carnallite
Answer :
Carnallite
Carnallite is $$KCl \cdot MgC{l_2} \cdot 6{H_2}O.$$
184.
The main difference between cast iron and pig iron is
A
cast iron is purest form of iron while pig iron is impure
B
cast iron has lower carbon content (3%) as compared to pig iron (4%) and is extremely hard and brittle
C
pig iron contains many impurities like $$S,P,Si$$ and $$Mn$$ while cast iron does not contain any impurity and can be casted into any shape
D
cast iron is soft and malleable while pig iron is extremely hard and brittle.
Answer :
cast iron has lower carbon content (3%) as compared to pig iron (4%) and is extremely hard and brittle
Pig iron contains about 4% $$C$$ and many other impurities like $$S,P,Si$$ and $$Mn.$$ Cast iron is made by melting pig iron with scrap iron and coke. It has slightly lower carbon content (3%) and is extremely hard and brittle.
185.
Consider the following isolation/purification processes :
(i) Heating impure metal with $${I_2}$$ at $${150^ \circ }C - {250^ \circ }C$$ and passing the resulting volatile iodide on hot tungsten filament at $${1400^ \circ }C$$ to get the pure metal.
(ii) Heating the sulphide ore in air until a part is converted to oxide and then further heating in the absence of air to let the oxide react with unchanged metal sulphide to get the metal.
(iii) Electrolysis of the molten electrolyte containing metal oxide and cryolite or fluorspar to obtain the metal.
The processes used for obtaining aluminium, titanium and lead 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)
$$\left( {\text{i}} \right)T{i_{\left( s \right)}}\left( {{\text{impure}}} \right) + 2{I_{2\left( g \right)}}$$ \[\xrightarrow{150-{{250}^{\circ }}C}Ti{{I}_{4}}\left( \text{volatile} \right)\] \[\xrightarrow[\text{Tungsten filamen}]{{{1400}^{\circ }}C}T{{i}_{\left( s \right)}}\left( \text{pure} \right)+2{{I}_{2\left( g \right)}}\]
$$\left( {{\text{ii}}} \right)2PbS + 3{O_2} \to 2PbO + 2S{O_2}$$
\[PbS+2PbO\xrightarrow[\text{temp}\text{.}]{\text{high}}3Pb+S{{O}_{2}}\]
$$\left( {{\text{iii}}} \right){\text{Cathode :}}\,A{l^{3 + }}\left( {{\text{melt}}} \right) + 3{e^ - }$$ $$ \to A{l_{\left( l \right)}}$$
$$\,\,\,\,\,\,\,\,\,\,{\text{Anode :}}\,{C_{\left( s \right)}} + {O^{2 - }}\left( {{\text{melt}}} \right)$$ $$ \to C{O_{\left( g \right)}} + 2{e^ - }$$
$$\,\,\,\,\,\,\,\,\,\,{C_{\left( s \right)}} + 2{O^{2 - }}\left( {{\text{melt}}} \right) \to $$ $$C{O_{2\left( g \right)}} + 4{e^ - }$$
186.
In this method, a low melting metal like tin can be made to flow on a sloping surface. In this way it is separated from higher melting impurities. The method is known as
A
distillation
B
vapour phase refining
C
liquation
D
zone refining
Answer :
liquation
No explanation is given for this question. Let's discuss the answer together.
187.
The metal that cannot be obtained by electrolysis of an aqueous solution of its salts is:
A
$$Ag$$
B
$$Ca$$
C
$$Cu$$
D
$$Cr$$
Answer :
$$Ca$$
On electrolysis of aqueous solution of $$s$$ - block elements $${H_2}$$ gas discharge at cathode.
At cathode: $${H_2}O + {e^ - } \to \frac{1}{2}{H_2} + O{H^ - }$$
188.
The ore that contains the metal in the form of fluoride is:
190.
In the electrolysis of alumina to obtain aluminium metal, cryolite is added mainly to
A
lower the melting point of alumina
B
dissolve alumina in molten cryolite
C
remove the impurities of alumina
D
increase the electrical conductivity
Answer :
lower the melting point of alumina
Fused alumina $$\left( {A{l_2}{O_3}} \right)$$ is a bad conductor of electricity. Therefore, cryolite $$\left( {N{a_3}Al{F_6}} \right)$$ and fluorspar $$\left( {Ca{F_2}} \right)$$ are added to purified alumina which not only make alumina a good conductor of electricity but also reduce the melting point of the mixture to around $$1140\,K.$$