Chemistry
State why aluminium is extracted from it's oxide by electrolysis while copper, lead, iron by reducing agents and mercury and silver by thermal decomposition.
Answer
Oxides of highly active metals like potassium, sodium, calcium, magnesium and aluminium have great affinity towards oxygen and so cannot be reduced by common reducing agents like carbon, carbon monoxide or hydrogen.
They are obtained by electrolytic reduction of fused metallic salts (halides and oxides) using inert electrodes.
The metals in the middle of the activity series such as iron, lead, copper, etc., are moderately reactive and are found as sulphides or carbonates in nature. They are obtained by the reduction of their oxides with carbon, carbon monoxide and hydrogen.
Mercury and silver are very less reactive, placed in the end of the reactivity series. The oxides of these metals are reduced to metals by heating alone.
Related Questions
(a) Some metallic oxides can be reduced by hydrogen, carbon, carbon monoxide and some cannot. Explain.
(b) Write balanced equation for the reduction of copper (II) oxide by hydrogen.
How are the following metallic oxides reduced. Write equations :
(a) Iron (II) oxide
(b) Zinc oxide
An ore on being heated in air forms sulphurous anhydride. Write the process used for the concentration of this ore.
(a) Define roasting. Name an ore on which roasting is done. Give balanced equation.
(b) Define calcination. Give an example and equation for calcination.