Tag: basics of metallurgy

Questions Related to basics of metallurgy

Which of the following metal oxides are reduced by CO?

chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

  1. ZnO

  2. Fe$ _2$O$ _3$

  3. CaO

  4. Al$ _2$O$ _3$

Show answer
Correct Option: A,B
Explanation:

Oxides of highly reactive metals cannot be reduced by $CO$. Hence $CaO$ and $Al _2O _3$ are not reduced by $CO$ and both $ZnO $ and $Fe _2O _3$ are reduced by $CO$

In which of the following chemical leaching is used either in the extraction of metal or in the concentration of ore?

chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

  1. Argentite

  2. Bauxite

  3. Alluvial sand containing gold

  4. All of these

Show answer
Correct Option: A

Which one of the following statements is incorrect about rock salt type?

chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

  1. It has fcc arrangement of $\mathrm { Na } ^ { + }$

  2. Nat and Cl-ions have a co-ordination number of $6:6$

  3. A unit cell of $NaCl$ consists of four $NaCl$ units

  4. All halides of alkali metals have rock-salt type structure

Show answer
Correct Option: D
Explanation:

The alkali halides crystallize in the NaCl structure also known as rock-salt structure (rock salt is the mineral form of sodium chloride); exceptions being CsCl, CsBr, and CsI, which crystallize in the CsCl structure. In the NaCl structure (face-centered cubic lattice), each cation is surrounding by six anions, and vice versa (coordination number of 6). In the CsCl structure, each cation is surrounded by eight anions and vice versa (coordination number of 8).

Option D is incorrect

The extraction of metals from oxide ores may involve:

chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

  1. reduction with carbon

  2. reduction with aluminium

  3. electrolyte reduction

  4. reduction with CO

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

These are the methods for extraction of metals from oxide ores:
Carbon reduction, involving reduction with CO or C
Self reduction
Thermite reduction, which employs Al
Electrolytic reduction.

The advantage(s) of using carbon to reduced a number of oxides and other compounds are :

chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

  1. easy availability of coke.

  2. low cost of carbon.

  3. tendency of carbon to show catenation..

  4. presence of carbon lowers the melting point of the oxide.

Show answer
Correct Option: A,B
Explanation:

The advantage(s) of using carbon to reduced a number of oxides and other compounds are
 (i) easy availability of coke.
 (ii) low cost of carbon.
 (iii) exothermic nature of reaction which requires less energy to keep the furnace hot.


Hence, A and B are the correct options. 

The extraction of metals from oxide ores involve :

chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

  1. reduction with carbon

  2. reduction with aluminium

  3. electrolyte reduction

  4. reduction with $CO$

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

During extraction of metals from oxide ores, the reduction of metal ore to crude metal can be carried out by using several methods such as pyrometallurgy, hydrometallurgy and electrometallurgy. Various reducing agents such as carbon, hydrogen, aluminum or other metals can be used. CO also reduces metal ores to crude metals.

Aluminothermy used for the spot welding of large iron structures is based upon the fact that :

chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

  1. As compared to iron, aluminium has greater affinity for oxygen.

  2. As compared to aluminium, iron has greater affinity for oxygen.

  3. Reaction between aluminium and oxygen is endothermic..

  4. Reaction between iron oxide and aluminium is exothermic.

Show answer
Correct Option: A,D
Explanation:

Aluminothermy used for the spot welding of large iron structures is based upon two facts 
(i) As compared to iron, aluminum has greater affinity for oxygen. hence, aluminum acts are reducing agent.
(ii) Reaction between iron oxide and aluminum is exothermic. High temperature is involved in the reaction.
Aluminum reduces iron oxide to iron. 

$Fe _2O _3 + 2 Al \rightarrow 2 Fe + Al _2O _3$

Oxides of the various metals are converted into metal by heating but not in :

chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

  1. $Ag _2O$

  2. CuO

  3. HgO

  4. all are correct

Show answer
Correct Option: B
Explanation:

Oxides of various metal oxides are converted into metals on heating but CuO (copper oxide) does not not converted into metal on heating but by reaction with Cu2S.

CuO + Heat$ \rightarrow$ no reaction
So, answer is B.

The methods chiefly used for the extraction of lead and tin from their ores are respectively _________________.

chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

  1. self reduction and carbon reduction

  2. self reduction and electrolytic reduction

  3. carbon reduction and self reduction

  4. cyanide process and carbon reduction

Show answer
Correct Option: A
Explanation:

The methods chiefly used for the extraction of lead and tin from their ores are respectively self reduction and carbon reduction. Self reduction for lead is as follows.
$2PbS+3O _2 \rightarrow 2PbO+2SO _2 \uparrow$
$PbS+2O _2 \rightarrow PbSO _4$
$2PbO + PbS \rightarrow 3Pb+SO _2 \uparrow$
$PbSO _4+PbS \rightarrow 2Pb+2SO _2 \uparrow$
Carbon reduction for tin is as follows.
$SnO _2+2C \rightarrow Sn+2CO \uparrow$

Which will not give metal on heating ?

chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

  1. $Ag _2CO _3$

  2. $ZnCO _3$

  3. $HgO$

  4. $CuO$

Show answer
Correct Option: B,D
Explanation:
A) $Ag _2CO _3(s)\rightarrow 2Ag(s) + CO _2(g) + O _2(g)$ on heating gives Ag(metal).
B) $ZnCO _3(s)\rightarrow ZnO(s) + CO _2(g)$ on heating  do not give metal it gives ZnO(zinc oxide).
C) $2HgO(heat)\rightarrow 2 Hg + O _2$ on heating gives Hg(metal).
D) CuO when heated in presence of sulfuric acid it also gives CuO again, hence CuO on heating do not give metal.
Hence option B and D are correct.