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CBSE Questions for Class 12 Engineering Chemistry General Principles And Processes Of Isolation Of Elements Quiz 9 - MCQExams.com
CBSE
Class 12 Engineering Chemistry
General Principles And Processes Of Isolation Of Elements
Quiz 9
Metallurgy involves steps:
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Concentration of ore
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Reduction of ore
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Purification
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alloy formation
Explanation
The extraction of metals from their ores involves the following majoor steps:
1.Crushing of the ore
2.Concentration of the ore
3.Reduction or isolation of the crude metal from its ore
4.Purification or refining of the metal.
Hence, the correct ans is (A),(B) and (C).
$$ACl_2 +BCl_2 \longrightarrow ACl_4 +B \downarrow$$
(Excess)
$$BO\xrightarrow [ ]{ Heat } B+\dfrac12{ O }_{ 2 }$$
($$A$$ and $$B$$ are metals.)
Their ore of $$B$$ is :
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cinnabar
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azurite
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galena
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siderite
Explanation
$$ACl_2 +BCl_2 \longrightarrow ACl_4 +B \downarrow$$
(Excess)
In this reaction, we can see that the oxidation number of A changes from +2 to +4. So, A should be Sn.
$$BO\xrightarrow [ ]{ Heat } B+\dfrac12{ O }_{ 2 }$$
The oxidation number of B changes from +2 to 0. B should be less reactive metal. So it is Hg. The ore of Hg is cinnabar.
Option (A) is correct.
Which of the following is correct processes ?
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$$Fe+Al_2O_3 \longrightarrow 2Al +Fe_2O_3$$
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$$ZnO +C\longrightarrow Zn +CO$$
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$$Cr_2O_3 +2Al \longrightarrow 2Cr +Al_2O_3$$
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$$2[Ag(CN)_2]^- +Zn \longrightarrow 2Ag +[Zn (CN)_4]^{2-}$$
Auto-reduction process is used for the extraction of :
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$$Cu$$
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$$Hg$$
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$$Pb$$
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$$Al$$
Explanation
Self-reduction method which is also known as auto-reduction method .The sulphide ore are heated in the air and a part of these is changed into oxide or sulphate then that reacts with the remaining part of the sulphide ore to give its metal.
This method is used for less electropositive metals i.e. Hg, Pb,Cu ,Sb.
Hence, correct option is (A),(B) and (C).
Consider the following statements :
Roasting is carried out to:
convert sulphide into oxide
melt the ore
remove moisture, water of hydration and expel organic matter
remove sulphur and arsenic in the form of volatile oxides
Out of these statements:
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$$1, 3$$ and $$4$$ are correct
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$$1, 2$$ and $$3$$ are correct
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$$2, 3$$ and $$4$$ are correct
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$$1, 2$$ and $$4$$ are correct
Explanation
ROASTING
The removal of the excess sulphur contained in sulphide ores by heating in an excess of air is called roasting. The concentrated sulphide ore is heated in reverberatory furnace, below its melting point or fusion temperature in the presence of an excess of air with or without the addition of an external substance.
In roasting definite chemical like oxidation, chlorination etc. take place but in calcination does not occur any major chemical changes.
Advantages of Roasting :
(i) Excess of sulphur is removed as volatile oxide.
(ii) The metal sulphide is converted into metal oxide and sulphate.
(iii) Impurities of arsenic and antimony are removed as their volatile oxides.
Hence , option A is correct .
In Hall's process, the ore is mixed with
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coke
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calcium carbonate
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sodium hydroxide
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sodium carbonate
Explanation
Hall's process is used for the extraction of Aluminum from Alumina.
Bauxite is concentrated through Hall’s process, in which sodium aluminate is prepared using sodium carbonate in bauxite. When excess carbon dioxide is passed through sodium aluminate in the presence of water, it forms aluminum hydroxide along with sodium carbonate. When dried aluminum hydroxide is ignited, alumina is formed.
The reaction involved in Hall's process is as follows:
$$Al_2O_3.2H_2O+2Na_2CO_3→2NaAlO_2+CO_2+2H_2O$$
Option D is correct.
Which of the following elements occurs in native state?
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$$I$$
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$$S$$
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$$Si$$
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$$P$$
The electrolytic reduction method for extraction of aluminium was discovered by:
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Hoope
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Hall and Halvoult
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Baeyer
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Serpeck
Explanation
The process of extracting Aluminium from Alumina $$Al_2O_3$$
by electrolysis is called Hall-Heroult process. In this process Aluminium is produced at cathode which is obtained by outlet, oxygen is released at an anode. It reacts with carbon of anode producing $$CO$$
and $$CO_2$$
.
Hence, the correct option is (B).
Alumina is not used as
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refractory material
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a medium in chromatography
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abrasive
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a white pigment
Which of the following elements is /are present in the anode mud in electrolytic refining of copper?
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Selenium
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Tellurium
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Silver
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Gold
Explanation
In the electrolytic refining of copper, the anode mud contains antimony, selenium, tellurium, silver, gold and platinum. These are impurities in blister copper. They are less reactive and unaffected by $$ CuSO_{4} - H_{2}SO_{4} $$solution and hence, settle down under anode as anode mud.
Hence, all options are correct.
Identify the correct statements:
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$$FeSO_4.(NH_4)_2SO_4.6H_2O$$ is called alum
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The mixture $$NH_4NO_3 +Al$$ powder is used as an explosive
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Anhydrous $$AlCl_3$$ is obtained when $$HCl$$ is passed over aluminum
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When $$Al$$ is heated with potassium hydroxide solution, hydrogen is evolved
Which of the following is not correctly matched?
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Red bauxite - Purification by Serpecks method.
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Iron from haematite - Carbon monoxide reduction
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Calamine - Carbonate ore
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$$FeSiO_{3}$$ - Slag obtained in the extraction of copper.
Explanation
Red bauxite container the impurities of iron oxides, titanium oxide and silica which are removed by Baeyer's and Hall's processes. Serpeck's method is used when bauxite contains only the impurity of silica.
Hence, option A is correct.
A substance which reacts with gangue to form fusible material is called
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Flux
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Catalyst
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Ore
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Slag
Explanation
(Impurity) Gangue + flux $$\rightarrow $$ Slag
Infusible Fusible
Option A is correct.
In our country, iron is obtained from the ore:
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cassiterite
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azurite
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haematite
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cryolite
Explanation
In our country, iron is obtained from the ore haematite. Haematite is considered to be the most important iron ore because of its high-grade quality and lumpy nature. About 59% of haematite ore deposits are found in the Eastern Sector.
Hence, option C is correct.
Which of the following metal is not found in free state
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$$Na$$
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$$Au$$
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$$Ag$$
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$$Pb$$
Explanation
$$Na$$ is alkali metal highly reactive. Hence present in combined state.
In froth floatation process, for the purification of ores, the particles of the ore float because:
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they are light
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they are insoluble
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they bear electrostatic charge
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their surface is not easily wetted by water
Naturally occurring substances from which a metal can be profitably (or economically) extracted are called
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Minerals
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Ores
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Gangue
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Salts
Explanation
Naturally occurring substances from which a metal can be profitably (or economically) extracted are called Ores.
Hence, Option B is correct answer.
For which ore of the metal , forth floatation method is used for concentration
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Horn silver
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Bauxite
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Cinnabar
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Haematite
Explanation
Cinnabar $$(HgS)$$ the ore of mercury is concentrated by froth floatation process.
The method of zone refining of metals is based on the principle of
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greater solubility of the impurity in the molten state than in the solid
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greater mobility of the pure metal than that of the impurity
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higher melting point of the impurity than that of the pure metal
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greater noble character of the solid metal than that of the impurity
Explanation
Zone refining of metals is based on the principle of
greater solubility of the impurity in the molten state than in the solid.
Hence, Option "A" is the correct answer.
Froth floatation process is used for concentration of
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Chalcopyrite
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Bauxite
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Haematite
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Calamine
Explanation
Froth Floatation process is used for the purification of metals containing sulphur.
Chalcopyrite contains sulphur that's why it is concentrated by froth floatation process.
Carbon monoxide reacts with iron to form
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$$ Fe(CO)_5 $$
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$$ FeCO_2 $$
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$$ FeO + C $$
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$$ Fe_2O_3 +C $$
Explanation
Carbon monoxide reacts with iron to form $$Fe_2O_3$$ and $$C.$$
$$ 2Fe + 3CO \quad \xrightarrow {Heat} \quad Fe_2O_3 +3C $$
General method for the extraction of metal from oxide ore is
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Carbon reduction
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Reduction by aluminium
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Reduction by hydrogen
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Electrolytic reduction
Explanation
Carbon reduction , $$Fe_2O_3 + 3C \rightarrow 2 Fe + 3CO$$
Which element is found in free state ?
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Iodine
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Sulphur
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Phosphorus
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Magnesium
Explanation
Among the following options, only Sulphur is found in its free state i.e. $$S_8$$.
Hence, Option "B" is the correct answer.
Write true or false for the following statements :
Those mineral which contain a very high percentage of a particular metal and from which metal can be profitably extracted are called ores.
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True
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False
Explanation
Ores are the minerals that contains very high percentage of particular metal and from which metals can be profitably extracted.
Which occurs in nature in free state?
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Fe
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Co
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Ni
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Pt
Explanation
Pt metal occurs in nature in free state because Pt is a noble metal.
Which one of the following is Fluorspar?
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$$CaF_2$$
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$$CaO$$
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$$H_2F_2$$
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$$CaCO_3$$
Explanation
$$CaF_2$$ is called Flourspar.
Hence, Option "A" is the correct answer.
The important step in the extraction of metal from carbonate ore is
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Calcination
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Roasting
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Electro - reduction
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Cupellation
Explanation
Calcination is an important in the extraction process $$ZnCO_3 \rightarrow ZnO + CO_2$$
Option A.
Which of the following metals exist in their native state in nature?
(i) $$Cu$$
(ii)$$Au$$
(iii)$$Zn$$
(iv)$$Ag$$
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(i) and (ii)
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(ii) and (iii)
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(ii) and (iv)
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(iii) and (iv)
Explanation
Hint: Metals with the least chemical reactivity exist in their native state.
Step 1:
Metals that are placed at the bottom of the reactivity series do not undergo chemical reaction under normal conditions and are inert. This is because those metals' valence electrons are not easily available for chemical reactions.
Step 2:
Metals like gold, silver, platinum, etc. are placed at the bottom of the reactivity series because of their inertness to the chemical reactions. So, they are generally found in their native state in nature. Reactive metals are generally found in combined states as compounds.
Step 3:
Among the given elements, copper and zinc are found in a combined state because of their comparatively higher reactivity but gold (Au) and silver (Ag) are found in their native state.
Final step:
So, the correct option is
(C) (ii) and (iv).
A mineral is usually associated with a large amount of unwanted material called :
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Gangue
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Flux
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Slag
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Ore
Explanation
A mineral is usually associated with a large amount of unwanted material called Gangue.
Hence, Option "A" is the correct answer.
Which one of the following elements is most abundant is earth crust ?
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Aluminium
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Silicon
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Carbon
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Oxygen
Explanation
Oxygen is the most abundant element in the earth's crust.
Hence, Option "D" is the correct answer.
Which one of the following types of metals is expected to occur in the native state ?
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The alkali metals
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The alkaline earth metal
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The noble metal
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The rare earth metals
Explanation
Noble metals are expected to occur in native state because of their low reactivity with other elements.
Hence, Option "C" is the correct answer.
Cinnabar is the ore of :
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Zn
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Cd
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Hg
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Ag
Explanation
Cinnabar is
HgS
.
Hence, Option "C" is the correct answer.
Highly electropositive metal (s) can not be commercially extracted by carbon reduction process at high temperature because these :
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metal combine with carbon to form covalent carbide
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metal combine with carbon to form ionic carbide
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$$ G_{f} $$ of highly electropositive metal oxide is having low negative value
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Consider the following reaction at $$ 1000^{0} C $$
Explanation
As they are highly electropositive metals, high purity metal is obtained at cathode. They are not extracted through carbon reduction because they aren't reduced. It they are reduced also, They have impurities.
The metal combines with carbon to form ionic carbide
Three most occurring elements into the earth crust are :
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O ,Si,A1
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Si, O , Fe
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Fe , Ca , A1
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Si , O , N
Explanation
Three most occurring elements into the earth crust are O, Si & Al.
Hence, Option "A" is the correct answer.
Froth floatation process is used for the concentration of the ore of :
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Fe
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A1
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Cr
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Cu
Explanation
Froth floatation process is used for the concentration of the ore of Cu.
Hence, Option "D" is the correct answer.
In zone refining method , the molten zone :
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consist of impurities only
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contains more impurities than the original metal
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contains the purified metal only
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moves to either side
Explanation
Zone-refining process is a group of similar methods of purifying crystals, in which a narrow region of a crystal is melted, and this molten zone is moved along the crystal. The molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind it as it moves through the ingot. It typically contains more impurity than the original metal.
Hence the correct option is B.
Which of thew following pair is correctly matched ?
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Copper - Oxidative refining
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Nickel - Kroll's process
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Mercury - Distillation
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Lead - van Arkel method
Explanation
Of the above matches, only Mercury is matched incorrectly. It should be matched with Amalgamation.
Hence, Option "C" is the correct answer.
In which of the following metallurgy, no reduction agent is required from outside ?
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Mercury from cinnabar
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Zinc from zinc blende
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Iron from heamatite
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Aluminium from Bauxite
Explanation
In case of metallurgy of
Mercury from Cinnabar, there is no requirement of reducing agent from outside because Mercury undergoes self-reduction.
Hence, Option "A" is the correct answer.
The method of zone refining of metals is based on the principle of :
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Greater mobility of the pure metal than that of impurity
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Higher melting point of the impurity than that of impurity
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Greater noble charcter of the solid meta than that of the pure metal
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Greater solubility of the impurity in the molten state than in the solid
Explanation
The method of zone refining of metals is based on the principle "
Greater solubility of the impurity in the molten state than in the solid
"
Hence, Option "D" is the correct answer.
Copper is extracted from sulphide ore using the method :
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carbon reduction
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carbon monoxide reduction
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auto reduction
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none of this
Explanation
Copper is extracted from sulphide ore using the method
auto reduction.
Hence, Option "C" is the correct answer.
In the alumino-thermite process, Al metal acts as :
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Oxidizing agent
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Reducing agent
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Flux
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Gangue
Explanation
In the alumino-thermite process, Al metal acts as a Reducing agent.
Hence, Option "B" is the correct answer.
Froth floatation process for the concentration of sulphide ores is an illustration of the practical application of :
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adsorption
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absorption
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sedimentation
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coagulation
The advantage of using carbon to reduce a number of oxides and other compounds are :
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easy availability of coke
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low cost of carbon
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tendency of carbon to show catenation
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presence of carbon lowers the melting point of the oxides
Explanation
The advantage of using carbon to reduce a number of oxides and other compounds are the
easy availability of coke &
low cost of carbon.
Hence, Options "A" & "B" are the correct answers.
For which of following metals, the carbon reduction cannot be used
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Lead
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Manganese
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Tungsten
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Iron
Explanation
The carbon reduction cannot be used for manganese and tungsten. This is because manganese and tungsten react with carbon to form manganese carbide and tungsten carbide respectively.
The function of adding cryolite in the electrolytic reduction of alumina by Hall-Heroult process is to :
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dissolve alumina
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lower the melting point of alumina
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lower the fuel bill
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increase the electrical conductivity of alumina
Explanation
In the electrolyte reduction of alumina by Hall-Heroult process, when cryolite is added, the melting point of alumina is lowered which also lowers the fuel bill. Also the electrical conductivity of alumina lowered.
Hence, options A, B, C and D are correct.
The disadvantage of carbon reduction method are :
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high temperature needed is expensive and requires the use of a blast furnace
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many metals combine with carbon forming carbides
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Carbon combines with oxygen to form poisonous CO
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Carbon cannot be used with highly electropositive metals
Explanation
The disadvantage of carbon reduction method are
(i) high temperature needed which is expensive and requires the use of a blast furnace
(ii) many metals combine with carbon forming carbides
(iii) carbon dioxide gas is released in the process which is green house gas.
(iii) metals produced contain significant amount of carbon. hence, metals obtained cannot be very pure.
Pick up the correct statement (S) :
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All minerals are ores
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All minerals cannot be an ore
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All ores are minerals
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The minerals from which can be extracted profitably are called ores
Explanation
Minerals from which metal can be extracted economically are called ores. So, all ores are minerals but vice versa not true.
Hence, Options "B", "C" & "D" are the correct answers.
Froth floatation process is used to concentrate which type of ores?
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Sulphide ores
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Phosphate ores
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Silicate ores
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Oxide ores
Explanation
The types of ores that can be concentrated by froth floatation process are sulphides ores. Froth floatation is method that is used to separate materials on the basis of their orientation towards water i.e. hydrophilic or hydrophobic.
The metal which always exists in free or native state is
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$$Au$$
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$$Ag$$
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$$Cu$$
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$$Na$$
Explanation
gold (Au)
Those natural occurring components from which element can be extracted profitably and conveniently known as
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Minerals
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Gangue
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Ores
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Flux
Explanation
The naturally occurring compounds of metals that are found in earth's crust along with some impurities are called minerals. An ore is the mineral from which the metal can be extracted profitably and conveniently.
hence C isc correct
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