Ores and Metallurgy MCQ Questions & Answers in Inorganic Chemistry | Chemistry
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1.
Purification of silicon element used in semiconductors is done by
A
zone refining
B
heating
C
froth floatation
D
heating in vacuum
Answer :
zone refining
Silicon is purified by zone refining . Metals of high purity are always purified by zone refining.
2.
Four metals and their methods of refinement are given
(i) $$Ni,Cu,Zr,Ga$$
(ii) electrolysis, van Arkel process, zone refining Mond's process
Choose the right method for each
A
$$Ni :$$ Electrolysis, $$Cu :$$ van Arkel process, $$Zr :$$ Zone refining, $$Ga :$$ Mond's process
B
$$Ni :$$ Mond's process, $$Cu :$$ Electrolysis, $$Zr :$$ van Arkel process, $$Ga :$$ Zone refining
C
$$Ni :$$ Mond's process, $$Cu :$$ van Arkel process, $$Zr :$$ Zone refining, $$Ga :$$ Electrolysis
D
$$Ni :$$ Electrolysis, $$Cu :$$ Zone refining, $$Zr :$$ van Arkel process, $$Ga :$$ Mond's process
Answer :
$$Ni :$$ Mond's process, $$Cu :$$ Electrolysis, $$Zr :$$ van Arkel process, $$Ga :$$ Zone refining
No explanation is given for this question. Let's discuss the answer together.
3.
In metallurgical process, aluminium acts as
A
an oxidising agent
B
a reducing agent
C
acidic flux
D
basic flux
Answer :
a reducing agent
Metals like $$Al,Na,K,Mg$$ act as reducing agents in metallurgical processes.
4.
Which of the following reactions is an example of autoreduction?
A
$$F{e_3}{O_4} + 4CO \to 3Fe + 4C{O_2}$$
B
$$C{u_2}O + C \to 2Cu + CO$$
C
$$Cu_{\left( {aq} \right)}^{2 + } + F{e_{\left( s \right)}} \to C{u_{\left( s \right)}} + Fe_{\left( {aq} \right)}^{2 + }$$
D
$$C{u_2}O + \frac{1}{2}C{u_2}S \to 3Cu + \frac{1}{2}S{O_2}$$
The sulphide ores of certain less electropositive metals like those of $$Hg,Pb,Cu,$$ etc. when heated in air bring about the conversion of a part of the sulphide ore to oxide or sulphate which then reacts with the remaining sulphide to give the metal and $$S{O_2}.$$ No external reducing agent is used in this process.
$$\eqalign{
& 2C{u_2}S + 3{O_2} \to 2C{u_2}O + 2S{O_2} \cr
& 2C{u_2}O + C{u_2}S \to 6Cu + S{O_2} \cr} $$
5.
Which one of the following is a mineral of iron?
A
Malachite
B
Cassiterite
C
Pyrolusite
D
Magnetite
Answer :
Magnetite
$$\eqalign{
& {\text{Mineral}}\,\,\,\,\,\,\,\,\,\,\,{\text{Chemical}}\,\,{\text{composition}} \cr
& {\text{Malachite}}\,\,\,\,\,\,\,\,CuC{O_3}.Cu{\left( {OH} \right)_2} \cr
& {\text{Cassiterite}}\,\,\,\,\,\,\,\,Sn{O_2} \cr
& {\text{Pyrolusite}}\,\,\,\,\,\,\,\,Mn{O_2} \cr
& {\text{Magnetite}}\,\,\,\,\,\,\,\,Fe{O_4} \cr
& {\text{Thus, magnetite is a mineral of iron}}{\text{.}} \cr} $$
6.
Which of the following statements regarding metallurgy of iron is incorrect ?
A
Reaction $$F{e_3}{O_4} + 4CO \to 3Fe + 4C{O_2}$$ belongs to lower temperature range $$(500 – 800K)$$ of the blast furnace.
B
Reaction $$FeO + CO \to Fe + C{O_2}$$ belongs to higher temperature range $$(900 – 1500K)$$ of the blast furnace.
C
The iron obtained from blast furnace is cast iron with $$3\% $$ carbon.
D
For reduction of iron oxide to occur $$\Delta G$$ of the couple of following reactions should be negative
$$\eqalign{
& FeO\left( s \right) \to Fe\left( s \right) + \frac{1}{2}{O_2}\left( g \right) \cr
& C\left( s \right) + \frac{1}{2}{O_2}\left( g \right) \to CO\left( g \right) \cr} $$
Answer :
The iron obtained from blast furnace is cast iron with $$3\% $$ carbon.
The iron obtained from blast furnace is pig iron with $$4\% $$ carbon and impurities like $$S, P, Mn$$ etc., in small amount.
7.
_______ and _______ are alloys of copper.
A
Brass, bronze
B
Brass, alloy steel
C
Copper pyrites, malachite
D
Copper glance, cuprite
Answer :
Brass, bronze
Brass is $$Cu + Zn$$ and bronze is $$Cu + Sn.$$
8.
Iron is obtained on large scale from $$F{e_2}{O_3}$$ by
9.
Which of the following pair is incorrectly matched?
A
Magnetite $$ - F{e_3}{O_4}$$
B
Copper glance $$ - C{u_2}S$$
C
Calamine $$ - ZnC{O_3}$$
D
Zincite $$ - ZnS$$
Answer :
Zincite $$ - ZnS$$
Zincite is $$ZnO.$$
10.
From the Ellingham graph between Gibbs energy and temperature, out of $$C$$ and $$CO$$ which is a better reducing agent for $$ZnO?$$
A
Carbon
B
$$CO$$
C
Both of these
D
None of these
Answer :
Carbon
The free energy of formation $$\left( {\Delta {G^ \circ }} \right)$$ of $$CO$$ from $$C$$ becomes lower at temperatures above $$1180\,K$$ whereas that of $$C{O_2}$$ from $$C$$ becomes lower above $$1270\,K$$ than $${\Delta {G^ \circ }}$$ of $$ZnO.$$ However, $${\Delta {G^ \circ }}$$ of $$C{O_2}$$ from $$CO$$ is always higher than that of $$ZnO.$$ Hence, $$C$$ can reduce $$ZnO$$ to $$Zn$$ but not $$CO.$$