Tag: general principles of metallurgy

Questions Related to general principles of metallurgy

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

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

  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

Show answer
Correct Option: C
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.

Which of the following statement is correct?

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

  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

Show answer
Correct Option: A,D
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.

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:

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

  1. $FeS + Cu _2S$

  2. $FeS + Cu _2O$

  3. $FeO + Cu _2S$

  4. $FeS+Cu _2S \rightarrow FeO+Cu _2O$

Show answer
Correct Option: D
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 
$FeS+Cu _2S \rightarrow FeO+Cu _2O$

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

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

  1. Cuprous sulphide

  2. Ferrous oxide

  3. Ferrous sulphide

  4. Cuprous oxide

Show answer
Correct Option: B
Explanation:

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

$FeO + SiO _2 \rightarrow FeSiO _3$

Anode mud obtained after electrolytic refining of copper contains:

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

  1. $Ag$

  2. $Au$

  3. $Pt$

  4. All of the above

Show answer
Correct Option: D
Explanation:
Electrorefining:
Anode: Impure copper or crude copper
Cathode: Pure copper
Electrolyte: 15% $CuSO _4$ Solution + 5% $H _2SO _4$

When electric current is passed through the electrolyte, the anode gradually dissolves and pure copper is deposited on the cathode which gradually grows in size. Impurities like. Fe, Zn, Ni etc, dissolve in the solution as sulphates while gold, silver, platinum settle down below the anode as anode mud.

What is the process of leaching in case of low grade copper ores?

chemistry principles of metallurgy concentration of ore concentration of ores general principles of metallurgy

  1. Leaching is carried out with $NaOH$ and $O _2$

  2. Leaching is carried out with $NaCN$

  3. Leaching is carried out with acids in presence of $O _2$

  4. Leaching is carried out by boiling the ore with water

Show answer
Correct Option: C
Explanation:

Leaching of low grade copper ores is carried out with acid or bacteria, when copper goes into solution as $Cu^{2+} _{(aq) }+ H _{2(g)}\rightarrow Cu _{(s)}+2H^+ _{(aq)}$ 

How do we separate two sulphide ores by froth floatation method?

chemistry principles of metallurgy concentration of ore concentration of ores general principles of metallurgy

  1. By using excess of pine oil.

  2. By adjusting proportion of oil to water or using depressant.

  3. By using collectors and froth stabilities like xanthates.

  4. By using some solvent in which one of the sulphides is soluble.

Show answer
Correct Option: B
Explanation:

By using depressants or adjusting proportion of oil to water, selective prevention of one sulphide ore from coming to the froth is possible.

An ore of tin containing, $FeCrO _4$ is concentrated by:

chemistry principles of metallurgy concentration of ore concentration of ores general principles of metallurgy

  1. gravity separation

  2. magnetic separation

  3. forth floatation

  4. leaching

Show answer
Correct Option: B
Explanation:
  • Magnetic separation based on differences in magnetic properties of the ore components.
  •  If either the ore or the gangue is attracted towards the magnetic field, then the separation is carried out by this method. 
  • For example, iron ores are attracted towards the magnet, hence, non–magnetic impurities can be separated from them using magnetic separation.
  • Here,$FeCrO _4$ being an iron ore can be separated by magnetic separation.

Removal of the unwanted materials like sand, clays, etc. from the ore is known as __, ___ or _____.

chemistry principles of metallurgy concentration of ore concentration of ores general principles of metallurgy

  1. concentration, dressing, benefaction

  2. separation, refining, gangue

  3. magnetic separation, Purification, gangue

  4. washing, refining, amalgamation

Show answer
Correct Option: A
Explanation:
  • Removal of the unwanted materials (e.g., sand, clays, etc.) from the ore is known as concentration, dressing or benefaction.

  • Before proceeding for concentration, ores are graded and crushed to a reasonable size. 

  • The concentration of ores involves several steps and the selection of these steps depends upon the differences in physical properties of the compound of the metal present and that of the gangue.

Which of the following ores cannot be concentrated by magnetic separation?

chemistry principles of metallurgy concentration of ore concentration of ores general principles of metallurgy

  1. Haematite

  2. Malachite

  3. Magnetite

  4. Siderite

Show answer
Correct Option: B
Explanation:
  • Magnetic separation based on differences in magnetic properties of the ore components.
  •  If either the ore or the gangue is attracted towards the magnetic field, then the separation is carried out by this method. 
  • For example, iron ores are attracted towards the magnet, hence, non–magnetic impurities can be separated from them using magnetic separation.
  • Here, Haematite, Magnetite, and Sidderite are iron ores and hence magnetic separation can be used to separate them.
  • Malachite is a Copper ore and hence magnetic separation can't be used to concentrate it.