plz answer fast
 

Dear student,
5 marks question :
1 the term calcination is defined as the heating of oxide ores in absence of air below its melting point.
e.g.  Heating of calcium carbonate ores : CaCO₃  $\stackrel{Heat }{\to }$ CaO  +  CO₂ ↑
2. The two metals which occur in free or native form in nature are gold ( Au )  and platinum ( Pt )
they can de refined by electro refining process .
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