Tag: production of metals

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
 (i) easy availability of coke.
 (ii) low cost of carbon.
 (iii) exothermic nature of reaction which requires less energy to keep the furnace hot.

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 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. 

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.

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.
$SnO _2+2C \rightarrow Sn+2CO \uparrow$

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

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.