Chemistry · Science General

Metallurgical Processes

1,436 Questions

This section explores key metallurgical processes including ore concentration, pyrometallurgy, and metal refining. It also covers corrosion and the properties of refractory materials. These chemistry questions are relevant for engineering and science entrance tests.

Pyrometallurgy furnacesMetal refining techniquesCorrosion protection methodsOre concentrationAuto reduction process

Metallurgical Processes Questions

Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy

When copper ore is mixed with silica, in a reverberatory furnace copper matte is produced. The copper matte contains:

  1. Sulphides of copper (II) and iron (II)

  2. Sulphides of copper (II) and iron (III)

  3. Sulphides of copper (I) and iron (II)

  4. Sulphides of copper (I) and iron (III).
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Copper matte is a mixture of cuprous sulphide (Cu2S) and ferrous sulphide (FeS). These are sulphides of copper (I) and iron (II).

Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy

The balance reaction involved during extraction of zinc from its ore, by calcination of zinc ore, is:

  1. $2ZnCO _{3} (s) \xrightarrow{Heat} 2ZnO(s) + CO _{2}(g)$
  2. $ZnCO _{3} (s) \xrightarrow{Heat} ZnO(s) + CO _{2}(g)$
  3. $ZnCO _{3} (s) \xrightarrow{Heat} 2ZnO(s) + CO _{2}(g)$

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Calcination is defined as heating to high temperatures in the presence of air or oxygen. Heating the metal carbonates result in the formation of metal oxides and carbon dioxide.
$ZnC{ O } _{ 3 }(s)\xrightarrow { heat } ZnO(s)+C{ O } _{ 2 }(g)$

Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy

$Cu _{2}S+2Cu _{2}O \rightarrow 6Cu+SO _{2}$
In which process of metallurgy of copper, above equation is involved -

  1. roasting

  2. self reduction

  3. refining

  4. purification
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

During the Bessemerisation process, the sulphide ores of less electropositive metals are heated in air to convert part of the ore into oxide or sulphate which then react with the remaining sulphide ore to give the metal and sulphur dioxide.
Copper sulphide is partially oxidised to cuprous oxide which futher can react with remaining copper sulphide to form copper and sulphur dioxide.
$2Cu _{2}S+3O _{2} \rightarrow 2Cu _{2}O+2SO _{2}$
$Cu _{2}S+2Cu _{2}O \rightarrow 6Cu+SO _{2}$
This process is also called  autoreduction process or air reduction process. 

Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy

In the extraction of copper, the copper matte is a mixture of:

  1. copper (II) sulphide and iron (II) sulphide

  2. copper (II) sulphide and iron (III) sulphide

  3. copper (I) sulphide and iron (II) sulphide

  4. copper (I) sulphide and iron (III) sulphide
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • The chemical formula of copper matte is $Cu _2S+FeS$. It is a combination of copper sulphide and iron sulphide.
  • It is a phase in which extracted metal is converted into crude metal which is a final product.
  • $80-70\%$ of copper matte is used $80-95\%$. $5- 17\%$ metallic copper, $Fe-Co$ alloy etc are used.
Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy

Metallurgical process of zinc involves roasting of zinc sulphide followed by reduction. Metallic zinc distills over as it is volatile and impurities like Cu, Pd and Fe gets condensed. The crude metal obtained is called spelter, which may be purified by:

  1. electrolysis process

  2. fractional distillation

  3. polling

  4. heating with iodine
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Explanation

Spelter Zn is purified by both distillation and electro fining process(here we get more pure Zn).

Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy

Blister copper is refined by stirring molten impure metal with green logs of wood because such wood liberates hydrocarbon gases (like $CH _{4}$). Name the process involved.

  1. Cupellation

  2. Poling

  3. Scaling

  4. Oxidation
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Blister copper contain $Cu _2O$ as impurity and is refined by poling process. 


In this process, the molten impure metal is stirred with green logs of wood because such a wood liberates hydrocarbon gases (like  $CH _{4}$), and hence, act as a reducing agent to reduce copper oxide to metal.


Option B is correct.

Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy

Self-reduction of CuS to Cu can be carried out in:

  1. Bessemer converter

  2. Pierce-Smith converter

  3. both (a) and (b)

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Self-reduction of CuS to Cu can be carried out in either Bessemer converter or Pierce-Smith converter.
$2Cu _2S+3O-2 \rightarrow 2Cu _2O + 2SO _2$
$2Cu _2O+Cu _2S \rightarrow 6Cu+SO _2$

Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy

Consider the following steps:

$CuS\,\overset{roast\,\,in\,\,air}{\rightarrow}\,(A)\, \overset{roast\,\,without\,\,air}{\rightarrow}\,(B)$

Which are the correct statements?

  1. It is self-reduction
  2. It involves disproportionation: $Cu _2S\,\rightarrow\,Cu\,+\,CuS$
  3. (A) is a mixture of $Cu _2O$ and $SO _2$ and (B) is $Cu$ and $SO _2$
  4. (A) is a mixture of $Cu$ and $SO _2$ and (B) is $CuSO _4$
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

Self-reduction of CuS to Cu can be carried out in either Bessemer converter or Pierce-Smith converter.

$2Cu _2S+3O _2 \rightarrow \underset {A} { 2Cu _2O + 2SO _2}$

$2Cu _2O+Cu _2S \rightarrow \underset {B} { 6Cu+SO _2}$

(A) is a mixture of $Cu _2O$  and $SO _2$ and (B) is  Cu and $SO _2$.

Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy
Lead metal is purified by electrolysis in a similar manner to copper; the electrolyte is lead (II) hexafluorosilicate $PbSiF _6$.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Lead metal is purified by electrolysis in a similar manner to copper, the electrolyte is Lead $(II)$ hexa Fluorosilicate $PbSiF _6$. The given statement is True.

A solution of Lead-Fluorosilicate containing an excess of fluorosilicic acid has been found to work satisfactorily as an electrolyte for refining lead. 

Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy

Froth-flotation process can be made more effective by the:

  1. use of pine oil which produces stable froth

  2. use of sodium ethyl xanthate as a collector that coats the particles of ore

  3. both (a) and (b)

  4. none of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pine oil acts as foaming agent. It stabilizes the froth.
Sodium ethyl xanthate (also potassium ethyl xanthate) acts as collectors.
They coat the ore particles.

Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy

Which of the following statement is correct?

  1. Froth flotation method can only be used for sulphide ore

  2. Tin stone consists of wolframite as non-magnetic impurity

  3. In cyanide process for the extraction of silver, Zn is used as leaching agent

  4. Bessemerization process is used in the extraction of copper from copper pyrite
Reveal answer Fill a bubble to check yourself
A,D Correct answer
Explanation

(A) Froth floatation method is used for concentration of sulphide ores such as galena $(PbS)$, zinc blende $(ZnS)$ and copper pyrites $(CuFeS _2)$.


(B) Tin stone consists of wolframite as magnetic impurity and stannic oxide as a non-magnetic impurity.

(C) In the cyanide process for the extraction of silver, Zn is used as leaching agent.
The ore containing silver or gold is leached with a dilute solution of NaCN or KCN in the presence of air. 


(D) Bessemerization process is used in the extraction of copper from copper pyrite.

The reactions involved in the process are given below.
$\displaystyle 2Cu _2S + 3O _2 \rightarrow 2Cu _2O + 2SO _2 \uparrow $
$\displaystyle 2Cu _2O + Cu _2S \rightarrow 6Cu + SO _2 \uparrow $

Thus, the options (A) and (D) are correct.

Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy

Copper is extracted from copper pyrites. After roasting, the ore is mixed with silica and coke and then smelted in a blast furnace. The matte obtained from the blast furnace is charged into a silica lined converter. Some silica is also added and a hot air blast is thrown into the mixture to obtain blister copper which is purified by electrorefining.


During roasting, copper pyrites are ultimately converted into a mixture of:

  1. $FeS + Cu _2S$
  2. $FeS + Cu _2O$
  3. $FeO + Cu _2S$
  4. $FeS+Cu _2S \rightarrow FeO+Cu _2O$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Process:
Copper pyrites contains only 2-3% of copper. The rest of ore contains iron as sulphide, silica, silicious materials, sulphur, arsenic etc as impurities. Froth floatation is carried out by xanthate and pine oil. The froth is collected and dried when concentrated ore is obtained which contains 25-30% of Cu. Then smelting of the roasted ore in blast furnace is done.

The minor reactions that occured during roasting continue here. Ferrous oxide combines with sand to form a fusible slag. Cuprous oxide formed combines with ferrous sulphide to give ferrous oxide and cuprous sulphide. This is because iron has more affinity for oxygen than copper. 
$FeO + SiO _2 \rightarrow FeSiO _3$

During roasting, copper pyrite converts into a mixture of 
$FeS+Cu _2S \rightarrow FeO+Cu _2O$
Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy

Silica is added to roasted copper ores during smelting in order to remove:

  1. Cuprous sulphide

  2. Ferrous oxide

  3. Ferrous sulphide

  4. Cuprous oxide
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Silica is added to roasted copper ores during smelting in order to remove $FeO$ (ferrous oxide) as $FeSiO _3$ (slag).

$FeO + SiO _2 \rightarrow FeSiO _3$