During the roasting of Zinc, sphalerite reacts with oxygen in air to produce ZnO

Question

During the roasting of Zinc, sphalerite reacts with oxygen in air to produce ZnO. ZnO is leached with sulfuric acid and then reduced electrolytically to zinc metal. the reactions involved are:

2ZnS(s)+3O2(g)-->2ZnO(s)+2SO2(g)

ZnO(s)+H2So4(l)-->ZnSO4(aq)+H2O(l)

2ZnSO4(aq)+2H2O(l)-->2Zn(s)+2H2SO4(l)+O2(g)

If a zinc refinery produces 150,000 metric tonnes of Zn metal (e.g. Zn(s)) per year from sphalerite. How much sphalerite is consumed during the year in metric tonnes? A) Assume 100% Efficiency. B) Assume 96% Efficiency.

Explanation / Answer

1) 2ZnS(s)+3O2(g)-->2ZnO(s)+2SO2(g)

2) 2 {ZnO(s)+H2So4(l)-->ZnSO4(aq)+H2O(l) }

3) 2ZnSO4(aq)+2H2O(l)-->2Zn(s)+2H2SO4(l)+O2(g)

from 1, 2 and 3 reactions it is concluded that 1 quantity of ZnS used to produce 1 quantity of Zn.

so

Zn produced is 150000 metric tones.

Zns used ??

atomic mass of Zn= 65.38 amu(atomic mass unit)

atomic mass of ZnS = 65.38 + 32.065 = 97.445 amu

65.38 amu ----- 150000 metric tones.

97.445 amu ---- ??

ZnS= 150,000 * 97.445/65.38

223566.075 metric tones of ZnS is required

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