Tag: chemistry

Quizzes (490) Questions (9892)

Questions Related to chemistry

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

Copper can he extracted by hydrometallurgy but not zinc because:

  1. Copper is comparatively less active metal as its reduction potential is high. It can be displaced from solutions of $Cu^{2+}$ ion by more active metals.
  2. Zn displaced from solution of $Zn^{2+}$ ion, a more reactive metal than it, but then readily react with water forming their corresponding ions and evolve hydrogen gas.

  3. Both (A) and (B) are correct.

  4. Copper can never be extracted by hydrometallurgy.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Hydrometallurgy involves formation of aqueous complex compounds and is used in extraction of less electro positive or less reactive metals like gold and silver. 


  • Copper is  also comparatively less active metal as its reduction potential is high and it can be displaced from solutions of $Cu^{2+}$ ion by more active metals.

  • $Zn$ can also be displaced from solution of $Zn^{2+}$ ion by a more reactive metal than it, but then readily react with water forming their corresponding zinc ions and evolve hydrogen gas.

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

Metals which can be extracted by smelting process is/are:

  1. $Sn$
  2. $Cu$
  3. $Zn$
  4. $Al$
Reveal answer Fill a bubble to check yourself
A,B,C,D Correct answer
Explanation

The process of extracting a metal from its oxide is known as 'smelting'. Most smelting processes involve direct reduction of the ore by carbon to metal and carbon dioxide. The production of primary aluminium is a good example of such a process.
Metals include copper, nickel, lead, zinc, silver, cobalt, gold, cadmium, etc.
Hence options A,B,C & D are correct.

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

Which of the following process involves smelting?

  1. ${2PbS+3O _2\rightarrow 2PbO+2SO _2}$
  2. ${Al _2O _3.2H _2O \rightarrow Al _2O _3+2H _2O}$
  3. ${Fe _2O _3+CO\rightarrow 2Fe+2CO _2}$
  4. ${Cr _2O _3+2Al\rightarrow Al _2O _3+2Cr+Heat}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Smelting : The process of extraction of metal in its molten state by any reducing agent in presence of flux is called smelting. 
For example : oxides of less electro - positive metals like Pb, Zn, Fe, Cu are reduced by any other reducing agents.
Reactions:
${Fe _2O _3+3CO\rightarrow  2Fe+3CO _2}$
Multiple choice thermodynamic principles of metallurgy general principles and processes of isolation of elements metallurgy chemistry

During the extraction of copper, the impurity (FeS) is removed as slag by mixing the contaminated copper ore with silica and coke. The molecular formula of slag is:

  1. $FeSiO _3$
  2. $Fe _2O _3$
  3. $FeSi\ (solid)$
  4. $FeSi\ (vapour)$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

During copper extraction, iron impurity (FeS) is removed by reacting it with silica (SiO2) to form iron silicate (FeSiO3), which is the slag.

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

Aluminum metal is frequently used as a reducing agent for the extraction of metal such as chromium or manganese from their respective _______

  1. zinc

  2. oxides

  3. reduction

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

Aluminium is more electropositive than Cr or Mn.
Hence, aluminum metal is frequently used as reducing agent for the extraction of metal such as chromium or manganese from their respective oxides.
The process of reduction is known as Aluminothermy. Thermite mixture $Fe _2O _3 + Al$ in 3:1 ratio is used.
$Cr _2 O _3 + 2Al       \rightarrow      Al _2O _3 + 2Cr$
$3 Mn _3 O _4 + 8 Al    \rightarrow     4 Al _2 O _3 + 9 Mn$

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

The metallurgical process in which a metal is obtained in a fused state is called:

  1. Smelting

  2. Roasting

  3. Calcination

  4. Froth floatation
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The process of extraction of metal in its molten state by any reducing agent in the presence of flux is called smelting. 

For example oxides of less electropositive metals like $Pb, Zn, Fe, Cu$ are reduced by any other reducing agents.

So, the correct option is $A$
Multiple choice thermodynamic principles of metallurgy general principles and processes of isolation of elements metallurgy chemistry

Which one is mismatched ?

  1. Poling - refining of copper

  2. Cupellation - refining of silver

  3. Smelting - An oxidation process

  4. Roasting - An oxidation process
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Poling: The molten impure metal (Cu) containing oxides as impurities is stirred with green poles of wood which releases hydrocarbon gases. The hydrocarbon gases reduces oxide to metal. It is used in refining of copper.

Cupellation: Pb present in Ag is removed by this method. The impure metal is heated in a cupel or oval shaped crucible made of bone ash or cement and blast of air is passed over the molten mass. The impurities get oxidised and removed with the blast of air. It is used in refining of silver.

Smelting: The process of extraction of metal in its molten state by any reducing agent in presence of flux is called smelting. For example: oxides of less electropositive metals like Pb, Zn, Fe, Cu are reduced by any other reducing agents. Thus, smelting is a reduction process and not an oxidation process.

Roasting: The process in which the concentrated ore is heated in blast of air and ore gets converted into oxide and impurities like sulphur, arsenic are also oxidised to their oxides and is removed is called Roasting. It requires very high temperature and specialized furnace like Bessemer or reverberatory furnace. Thus, it is an ixidation process.