Question

The chief ore of Zn is the sulphide, Zns. The ore is
concentrated by froth floatation process and then
heated in air to convert ZnS to Zno.

2ZnS + 30,- 80% 2 ZnO + 250

ZnO + H2SO, - 100% → ZnSO, +H, O

2 ZnSO, +2H20 80% +2 Zn+ 2H2SO4 + O2

The number of moles of ZnS.required for producing
2 moles of Zn will be:
(A) 3.125
(B) 2 0
(C) 2.125
(D) 4
​

Answer 1

Answer:

In the first reaction 2ZnS + 3O2 -> 2ZnO + 2SO2 we will get the number of moles of the ZnS will be 1.6moles as the reaction is completed only 80%.

For the second reaction ZnO + H2SO4 -> ZnSO4 + H2O the number of moles of ZnO is as usual 1.6moles and the number of moles of ZnSO4 will be also 1.6moles.

For the third reaction 2ZnSO4 + 2H2O -> 2Zn + 2H2SO4 + O2 the number of moles of the ZnSO4 is again 1.6moles and the moles of Zn thus is 1.28moles.

Hence, to form 1.28 moles of Zn we require 2moles of ZnO, then accordingly for 2 moles of Zn we will need ZnS as 2*2/1.28 moles = 3.125 moles of ZnS.