Ores and Metallurgy MCQ Questions & Answers in Inorganic Chemistry | Chemistry
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91.
Calcination is used in metallurgy for removal of ?
A
Water and sulphide
B
Water and $$C{O_2}$$
C
$$C{O_2}$$ and $${H_2}S$$
D
$${H_2}O$$ and $${H_2}S$$
Answer :
Water and $$C{O_2}$$
Calcination is used for removal of volatile impurities and decompose carbonates.
92.
During extraction of aluminium from bauxite,
A
the concentration of ore is done by gravity separation method
B
molten mixture of aluminium oxide, cryolite or fluorspar is electrolysed
C
impure aluminium is refined by liquation
D
molten aluminium is obtained at cathode while fluorine is liberated at anode
Answer :
molten mixture of aluminium oxide, cryolite or fluorspar is electrolysed
Purified $$A{l_2}{O_3}$$ is mixed with $$N{a_3}Al{F_6}$$ and $$Ca{F_2}$$ to improve conductivity of $$A{l_2}{O_3}$$ and to lower the melting point.
\[A{{l}_{2}}{{O}_{3}}\xrightarrow{\text{electrolysis}}2A{{l}^{3+}}+3{{O}^{2-}}\]
$$\eqalign{
& {\text{At cathode}}:A{l^{3 + }} + 3{e^ - } \to Al \cr
& {\text{At anode}}:\,\,\,C + {O^{2 - }} \to CO + 2{e^ - } \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C + 2{O^{2 - }} \to C{O_2} + 4{e^ - } \cr} $$
93.
Cassiterite is concentrated by
A
levigation
B
electromagnetic separation
C
floatation
D
liquefaction
Answer :
electromagnetic separation
Cassiterite contains the magnetic impurities of $$FeS{O_4}$$ and concentrated by electromagnetic separation.
94.
Which of the following reactions show the process of smelting?
95.
The chemical composition of ‘slag’ formed during the smelting process in the extraction of copper is
A
$$C{u_2}O + FeS$$
B
$$FeSi{O_3}$$
C
$$CuFe{S_2}$$
D
$$C{u_2}S + FeO$$
Answer :
$$FeSi{O_3}$$
NOTE : During the extraction of copper, iron is present in the ore as impurity $$\left( {FeS} \right)$$.
The ore together with a little coke and silica is smelted; $$FeS$$ present as impurity in the ore is oxidized to iron oxide, which then reacts with silica to form fusible ferrous silicate which is removed as slag.
$$2FeS + 3{O_2} \to 2FeO + 2S{O_2} \uparrow ;$$
$$FeO + Si{O_2} \to \mathop {FeSi{O_3}}\limits_{\left( {Slag} \right)} $$
96.
$${\Delta _f}{G^ - }$$ vs $$T$$ plot in the Ellingham diagram slopes downward for the reaction
A
$$Mg + \frac{1}{2}{O_2} \to MgO$$
B
$$2Ag + \frac{1}{2}{O_2} \to A{g_2}O$$
C
$$C + \frac{1}{2}{O_2} \to CO$$
D
$$CO + \frac{1}{2}{O_2} \to C{O_2}$$
Answer :
$$C + \frac{1}{2}{O_2} \to CO$$
$$C\left( s \right) + \frac{1}{2}{O_2}\left( g \right) \to CO\left( g \right);\Delta S$$ increases. Hence, as the temperature increases, $$T\Delta S$$ increases and hence $$\Delta G\left( {\Delta H - T\Delta S} \right)$$ decreases. In other words, the slope of the curve for formation of $$CO$$ decreases. However, for all other oxides, it increases.
97.
One of the processes used for concentration of
ores is $$Froth{\text{ }}floatation{\text{ }}process.$$ This process is
generally used for concentration of $$sulphide{\text{ }}ores.$$ Sometimes in this process we add $$NaCN$$ as a depressant. $$NaCN$$ is generally added in case of $$ZnS$$ and $$PbS$$ minerals. What is the purpose of addition of $$NaCN$$ during the process of Froth floatation ?
A
$$NaCN$$ causes reduction by precipitation
B
A soluble complex is formed by reaction between $$NaCN$$ and $$ZnS$$ while $$PbS$$ forms froth
C
A soluble complex is formed by reaction between $$NaCN$$ and $$PbS$$ while $$ZnS$$ forms froth
D
A precipitate of $$Pb{\left( {CN} \right)_2}$$ is produced while $$ZnS$$ remain unaffected.
Answer :
A soluble complex is formed by reaction between $$NaCN$$ and $$ZnS$$ while $$PbS$$ forms froth
$$NaCN + ZnS \to \mathop {N{a_2}\left[ {Zn{{\left( {CN} \right)}_4}} \right]}\limits_{{\text{Soluble complex}}} $$
A layer of this zinc complex is formed on the surface of $$ZnS$$ and due to this $$ZnS$$ is prevented from the froth formation while $$PbS$$ form froth. ( i.e., $$NaCN$$ is added as depressant for $$ZnS$$ )
98.
Which of the following pairs of metals is purified by van Arkel method ?
A
$$Ga$$ and $$In$$
B
$$Zr$$ and $$Ti$$
C
$$Ag$$ and $$Au$$
D
$$Ni$$ and $$Fe$$
Answer :
$$Zr$$ and $$Ti$$
\[\begin{align}
& Zr\text{ and }Ti\text{ are purified by van Arkel method}\text{.} \\
& \text{Zr}\left( s \right)+2{{I}_{2}}\left( g \right)\xrightarrow{870K}Zr{{I}_{4}}\left( g \right) \\
& Zr{{I}_{4}}\left( g \right)\xrightarrow[\text{Tugsten filament}]{2075K}Zr\left( s \right)+2{{I}_{2}}\left( g \right) \\
& Ti\left( s \right)+2{{I}_{2}}\left( s \right)\xrightarrow{523K}Ti{{I}_{4}}\left( g \right) \\
& Ti{{I}_{4}}\xrightarrow{1700K}\underset{\text{Pure titanium}}{\mathop{Ti\left( s \right)}}\,+2{{I}_{2}}\left( g \right) \\
\end{align}\]
99.
Magnesium oxide is used for the lining in steel making furnace because
A
$$MgO$$ acts as an acidic flux to remove impurities of $$Si, P$$ and $$S$$
B
$$MgO$$ acts as a basic flux to remove impurities of $$Si, P$$ and $$S$$
C
$$MgO$$ acts as an oxidising agent to remove impurities of oxides
D
$$MgO$$ does not react with any type of impurities
Answer :
$$MgO$$ acts as a basic flux to remove impurities of $$Si, P$$ and $$S$$
$$MgO$$ acts as a basic flux to remove impurities of $$Si,P$$ and $$S$$ through slag formation.
\[\underset{\begin{smallmatrix}
\text{Basic} \\
\text{flux}
\end{smallmatrix}}{\mathop{MgO}}\,+\underset{\begin{smallmatrix}
\text{Acidic} \\
\text{impurities}
\end{smallmatrix}}{\mathop{Si{{O}_{2}}}}\,\to \underset{\text{Slag}}{\mathop{MgSi{{O}_{3}}}}\,\]
$$\eqalign{
& 3MgO + {P_2}{O_5} \to M{g_3}{\left( {P{O_4}} \right)_2} \cr
& MgO + S{O_2} \to MgS{O_3} \cr} $$
100.
Roasting of sulphides gives the gas $$X$$ as a by-product. This is a colourless gas with choking smell of burnt sulphur and causes great damage to respiratory organs as a result of acid rain. Its aqueous solution is acidic acts as a reducing agent and its acid has never been insolated. The gas $$X$$ is
A
$${H_2}S$$
B
$$S{O_2}$$
C
$$C{O_2}$$
D
$$S{O_3}$$
Answer :
$$S{O_2}$$
$$S{O_2}$$ gas is obtained when any sulphide ore is toasted.
$$2{M_2}S + 3{O_2}\mathop \to \limits^\vartriangle 2{M_2}O + 2S{O_2}$$
This gas exhibits all the characteristics that are given in the question.