With the help of suitable chemical equations, list the two main differences between roasting and calcination…
With the help of suitable chemical equations, list the two main differences between roasting and calcination. How is metal reduced from the product obtained after roasting/calcination of the ore ? Write the chemical equation for the reaction involved.
Solution
Roasting vs Calcination:
1. It is carried out for sulphide ores. | It is carried out for carbonate ores.
2. Ore is heated in excess of air | Ore is heated in absence or limited supply of air.
2ZnS + 3O2 → 2ZnO + 2SO2 OR 2HgS + 3O2 $\xrightarrow{\text{Heat}}$ 2HgO + 2SO2 OR 2Cu2S + 3O2 $\xrightarrow{\text{Heat}}$ 2Cu2O + 2SO2 | ZnCO3 $\xrightarrow{\text{Heat}}$ ZnO + CO2 OR CaCO3 $\xrightarrow{\text{heat}}$ CaO + CO2 OR PbCO3 $\xrightarrow{\text{heat}}$ PbO + CO2
Reduction with the help of carbon
ZnO + C $\xrightarrow{\text{Heat}}$ Zn + CO
Alternate answer
With the help of heat
2HgO(s) $\xrightarrow{\text{Heat}}$ 2Hg(l) + O2(g)
OR
Auto reduction / Heating with its ore
2Cu2O + Cu2S $\xrightarrow{\text{Heat}}$ 6Cu(s) + SO2(g)
(or Any other)