Roasting and calcination
Turning ores into oxides.
Oxides are easier
It is easier to get a metal from its oxide than from its sulphide or carbonate.
So what must be done to sulphide and carbonate ores first?
What this lesson covers
The idea
Since a metal is easier to obtain from its oxide, sulphide ores are first converted to oxides by heating strongly in excess air (roasting) and carbonate ores by heating strongly in limited air (calcination).
Oxides are easier
It is easier to get a metal from its oxide than from its sulphide or carbonate.
So what must be done to sulphide and carbonate ores first?
- Convert them into oxides
- Nothing, use them as they are
- Mix them with sand
Roasting or calcination
Tap the process each statement describes.
Oxides first
It is easier to obtain a metal from its oxide than from its sulphide or carbonate. So these ores are first changed into oxides. Sulphide ores are heated strongly in excess air: roasting. Carbonate ores are heated strongly in limited air: calcination.
Since a metal is easier to obtain from its oxide, sulphide ores are first converted to oxides by heating strongly in excess air (roasting) and carbonate ores by heating strongly in limited air (calcination).
Notes
Roasting: sulphide ore heated strongly in excess air; calcination: carbonate ore heated strongly in limited air; both give oxides.
Check yourself
Heating a sulphide ore strongly in excess air to get the oxide is called ...
Heating a carbonate ore strongly in limited air to get the oxide is called ...
Why are sulphide and carbonate ores converted into oxides before reduction?
When zinc carbonate, ZnCO₃, is calcined, it gives zinc oxide and ...
- roasting — correct. Yes!
- calcination. Calcination is for carbonate ores, in limited air.
- refining. Refining is purifying the metal after extraction.
- roasting. Roasting is for sulphide ores, in excess air.
- calcination — correct. Yes!
- anodising. Anodising makes a thick oxide layer on aluminium.
- Oxides are free of impurities. The book gives the reason as it being easier to obtain a metal from its oxide.
- Oxides are lighter. The book gives the reason as it being easier to obtain a metal from its oxide.
- It is easier to obtain a metal from its oxide — correct. Yes!
- carbon dioxide — correct. Yes!
- sulphur dioxide. Sulphur dioxide is given by roasting a sulphide ore.
- hydrogen. The book's equation for ZnCO₃ gives ZnO and CO₂.