Tag: chemistry

Questions Related to chemistry

Chemical reactions of the hydrometallurgical extraction of copper is/are?

thermodynamic principles of metallurgy general principles and processes of isolation of elements metallurgy chemistry

  1. $CuO\, +\, H _2SO _4\, \rightarrow\, CuSO _4\, +\, H _2O$

  2. $CuCO _3\, +\, H _2SO _4\, \rightarrow\, CuSO _4\, +\, H _2O\, +\, CO _2$

  3. $Cu _2S\, +\, 2H _2SO _4\, +\, 2O _2\, \rightarrow\, 2CuSO _4\, +\, SO _2\, +\, 2H _2O$

  4. All of these

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Correct Option: D

Of the following reduction processes, correct processes are:

thermodynamic principles of metallurgy general principles and processes of isolation of elements metallurgy chemistry

  1. $Fe _2O _3\,+\,C\,\rightarrow\,Fe$

  2. $ZnO\,+\,C\,\rightarrow\,Zn$

  3. $Ca _3(PO _4) _2\,+\,C\,\rightarrow\,P$

  4. $PbO\,+\,C\,\rightarrow\,Pb$

Show answer
Correct Option: A,B,C,D
Explanation:

All the four processes are correct.
$ZnO+C\overset{1100^{0}C}{\rightarrow}Zn+CO$
$Fe _{2}O _{3}+3C\rightarrow 2Fe+3CO$
$Ca _3(PO _4) _2\,+\,C\,\rightarrow\,2P +3CaO + CO _2$
$PbO\,+\,C\,\rightarrow\,Pb +CO$

$AgCl$ (horn silver) is converted into $Ag$ by the pyrometallurgical method.

thermodynamic principles of metallurgy general principles and processes of isolation of elements metallurgy chemistry

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Pyrometallurgy is the process of extraction and purification involving the application of heat.

By this process chloride residues are smelted with an agent such as sodium silicate that provides alkali  metal oxide without generating gases, such as $CO _2$.
$2AgCl+Na _2O+SiO _2\longrightarrow Ag _2O+2NaCl+SiO _2$
$Ag _2O\longrightarrow 2Ag+\cfrac {1}{2}O _2$.

By annealing, steel :

thermodynamic principles of metallurgy general principles and processes of isolation of elements metallurgy chemistry

  1. becomes soft

  2. becomes liquid

  3. become hard and brittle

  4. is covered with a thin film of $Fe _3O _4$

Show answer
Correct Option: A
Explanation:

By annealing, steel becomes soft.


In anealing, steel is first heated to bright redness and then cooled slowly.

When $FeCr _2O _4$ is heated with carbon an alloy called ferrochrome is obtained.

thermodynamic principles of metallurgy general principles and processes of isolation of elements metallurgy chemistry

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Ferrochrome is produced by reduction of  $Cr-ore$ (an oxide of Chromium and iron) with coal and coke.

Ferrochrome is iron-chromium alloy. So, the statement "when $FeCr _2O _4$ is heated with carbon an alloy Ferrochrome is obtained" is correct.

In iron metallurgy, lime stone is used :

thermodynamic principles of metallurgy general principles and processes of isolation of elements metallurgy chemistry

  1. To obtain heat energy

  2. To reduce iron oxide into iron

  3. As an iron ore

  4. To remove sand ($SiO _2$)

Show answer
Correct Option: D
Explanation:

In the extraction of iron, the roasted ore is mixed with coke and lime stone (flux) and is then heated in the presence of air at high temperature in a furnace. Impurity of $SiO _2 $ is removed as calcium silicate $(CaSiO _3 slag)$.
$ CaCO _3\rightarrow CaO+CO _2$
$CaO+SiO _2\rightarrow CaSiO _3$

During smelting, an additional substance is added which combines with impurities to form a fusible product. It is known as :

thermodynamic principles of metallurgy general principles and processes of isolation of elements metallurgy chemistry

  1. Slag

  2. Mud

  3. Gangue

  4. Flux

Show answer
Correct Option: D
Explanation:

Flux is a substance which may be either acidic oxide $(Si{O} _{2})$ or basic oxide $(CaO, MgO)$. It combines with certain impurities (gangue particles) in order to form a substance called slag. This can be easily removed.

The pyrometallurgical operations involve the use of:

thermodynamic principles of metallurgy general principles and processes of isolation of elements metallurgy chemistry

  1. High temperature

  2. Sulphide ores

  3. Electrolysis

  4. Complexation

Show answer
Correct Option: A
Explanation:

Pyrometallurgy employs high temperatures to carry out smelting and refining operations to extract metals from their minerals. 


Hydrometallurgy uses aqueous solutions to separate the desired metals. Finally, electrometallurgy employs electrical energy to extract and refine metals.

Hydro-metallurgical process of extraction of metals is based on :

thermodynamic principles of metallurgy general principles and processes of isolation of elements metallurgy chemistry

  1. Complex formation

  2. Hydrolysis

  3. Dehydration

  4. Dehydrogenation

Show answer
Correct Option: A
Explanation:

Hydrometallurgy is a technique involving the use of aqueous chemistry for the recovery of metals from ores, concentrates, and recycled or residual materials. This process is used in extraction of less electro positive or less reactive metals like gold and silver by complex formation. 

For the pyrometallurgical method used for the extraction of copper from sulphide ore, which statement(s) is/are correct?

thermodynamic principles of metallurgy general principles and processes of isolation of elements metallurgy chemistry

  1. Pyrometallurgy is a dry method

  2. It involves concentration by leaching the sulphide ore with dil. $H _2SO _4$

  3. It involves concentration of the sulphide ore by froth flotation process

  4. It involves concentration by leaching for every ore

Show answer
Correct Option: A,C
Explanation:
The copper is extracted from sulphide ore by pyrometallurgy which involves reduction of the concentrated ore at high temperature.
This process is a dry process.
In this process, the sulphide ore is concentrated by froth floatation process.
In this process, the sulphide ore is not concentrated by leaching with dil sulphuric acid.
Thus, statements B  and D are incorrect and statement A and C are correct.