Question

The first step in the industrial recovery of zinc from the zinc sulfide ore is roasting, that is, the conversion of ZnS to ZnO by heating:

2𝑍𝑛𝑆(𝑠) + 3𝑂2(𝑔) → 2𝑍𝑛𝑂(𝑠) + 2𝑆𝑂2(𝑔) ∆𝐻 = −879 𝑘𝐽 𝑚𝑜𝑙

Calculate the heat evolved (in kJ) per gram of ZnS roasted

Answer 1

In this item, we are provided the heat released for each 2mols of ZnS is 879kJ

Amount of ZnS = 2mols of ZnS ×97.474g/mol = 194.9 g ZnS

Heat released = 879/194.9

= 4.5kJ/g