Basics of materials balance:

The elements of material balance are illustrated through a problem. Consider roasting of copper ore concentrate: and . It is roasted and the roasted ore has the following composition

 and

All copper in the roasted ore is as  and  partly oxidized to  and partly to . During roasting  of ore concentrate is used. Fuel is used and its amount is  of ore. Of the sulphur oxidized,  goes to  and  goes to . Find

1. Weight of roasted ore/ ton of concentrate and analysis of roasted ore.
2.  sulphur eliminated
3. Volume and composition of gases
4. Excess air used for combustion and roasting
   
   

Calculation procedure:

1. and of ore concentrate enter into roast product.
2. is oxidized to  and  depending on oxidizing condition.
3. In partial roasting, usually not all S of concentrate is oxidized.
4. Sulphur in the roast product is present as and .
5. In the roast product oxygen is in combined form either with  or with .
6. Theoretical amount of air can always be calculated once the reactants and products are specified. Here balanced chemical equation helps very often to calculate theoretical air.
7. 1 mole of air contains 0.21mols of  and 0.79mols of .1 mol of oxygen and 3.76mols of  forms 4.76mols.

To find weight of roasted ore one can do either  balance or  balance or even  balance.