Tag: extraction of metals from ore

Questions Related to extraction of metals from ore

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.

Which of the following metal oxide(s) gives metal and oxygen on heating ? 

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

  1. $ NaNO _3 $

  2. $ KNO _3 $

  3. $ Hg(NO _3) _2 $

  4. $ AgNO _3 $

Show answer
Correct Option: C,D
Explanation:

$ AgNO _3 \xrightarrow{\Delta} Ag + \frac {1}{2} O _2  +NO _2 $

$ Hg(NO _3) _2 \xrightarrow{\Delta}  Hg + O _2 +2NO _2 $

$4KNO _3(s)\xrightarrow{\Delta} 2K _2O(s)+2N _2(g)+5O _2(g)$

$4NaNO _3(s)\xrightarrow{\Delta} 2Na _2O(s)+2N _2(g)+5O _2(g)$

Selection of temperature to carry out a reduction process depends so as to make:

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

  1. $\Delta G$ negative

  2. $\Delta G$ positive

  3. $\Delta H$ negative

  4. $\Delta H$ positive

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Correct Option: A
Explanation:

When $\Delta$G is negative, a process or chemical reaction proceeds spontaneously in the forward direction and similar condition is required for a reduction process also. 

Auto reduction process is used for the extraction of:

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

  1. Cu

  2. Hg

  3. Pb

  4. Al

Show answer
Correct Option: A,B,C
Explanation:
Auto-reduction or air reduction is a very popular reaction in metallurgy. 

It is a process in which sulphide ores of less electropositive metals like Hg, Pb, Cu etc., are heated in the air so as to convert part of the ore into oxide or sulphate which then reacts with the remaining of sulphide ore in absence of air to give the metal and sulphur dioxide.

In which of the following isolations is no reducing agent required?

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

  1. Iron from haematire

  2. Tin from tin oxide

  3. Mercury from cinnabar

  4. Zine from zinc blende

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Correct Option: C
Explanation:

Cinnabar ore is relatively concentrated, it can be processed directly without any intermediate steps to remove waste material and without requirement of a reducing agent. 

The extraction of metals from oxide ores involve(s) :

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. electrolytic 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.

$H _2$ is not widely used as the reducing agent in metallurgic process because :

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

  1. many metals react with $H _2$ at elevated temperature forming hydrides

  2. there is a risk of explosion from $H _2$ and $O _2$ present in the air

  3. reducing power of $H _2$ does not increase with temperature

  4. reducing power of $H _2$, increases with temperature

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

$H _2$ is not widely used as the reducing agent in metallurgic process because metals react with $H _2$ at elevated temperature forming hydrides. When $H _2$ and $O _2$ present in the air are combined it will be explosive. Reducing power of $H _2$ does not increase with temperature, which is essential in metallurgy.