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Why are carbonate ores usually converted into oxides prior to the extraction of metals?
Reduction of metal oxides is easier than metal carbonates
Carbonates are highly soluble in water
Carbonates release toxic gases on heating
Oxides conduct electricity better
Reduction of metal oxides is easier than metal carbonates
Metals are extracted from their ores through reduction. It is thermodynamically and kinetically much easier to reduce metal oxides to their metallic state using reducing agents like carbon or carbon monoxide compared to reducing carbonates directly.
Metals are extracted from their ores through reduction. It is thermodynamically and kinetically much easier to reduce metal oxides to their metallic state using reducing agents like carbon or carbon monoxide compared to reducing carbonates directly.
Think of extracting metal like opening a door: an oxide is like an unlocked door that just needs a push, while a carbonate is like a door that is bolted shut; you must first remove the bolt (calcination) before you can push it open (reduction).
O-R-R: Ores to Oxide, then Reduce.
MCO3тАЛ╬ФтАЛMO+CO2тАЛ тАФ Calcination of metal carbonate
MO+CтЖТM+CO тАФ Reduction of metal oxide
Carbonate ores undergo calcination, where they are heated in the absence of air to release CO2тАЛ and leave behind metal oxides (MCO3тАЛ╬ФтАЛMO+CO2тАЛ). Once the metal oxide is obtained, it is reduced to pure metal using a reducing agent (MO+CтЖТM+CO). This two-step process is efficient because oxygen acts as a better leaving group during chemical reduction compared to the carbonate ion complex.
Calcination is the process of heating ores in the absence or limited supply of air.
Reduction is the removal of oxygen from the metal oxide.
Carbon acts as a common reducing agent in industrial metallurgy.
Higher yield of pure metal
More energy-efficient reduction process
Requires high temperatures for calcination
Generates CO2тАЛ gas emissions
Extraction of Zinc from Calamine (ZnCO3тАЛ)
Extraction of Lead from Cerussite (PbCO3тАЛ)
Calcination refers to heating carbonates, while roasting refers to heating sulfide ores in excess air.
Option B is incorrect because carbonate solubility does not govern the ease of metallurgical reduction.
Option C is incorrect because CO2тАЛ is generally considered an asphyxiant rather than a highly toxic industrial pollutant in this context.
Option D is incorrect because the electrical conductivity of the ore is not the deciding factor in chemical reduction methods.
A is correct тАФ Metal oxides are significantly more reactive and easier to reduce than metal carbonates during the smelting process.
In exams, remember that sulfide ores are always 'Roasted' (in air) while carbonate ores are always 'Calcined' (in absence of air) to obtain the oxide.
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