The mass fraction of zinc in (zinc sulfide) is …

Zinc sulphide formula – ZnS.
Zinc sulfide is unstable in humid air (oxidizes to sulfate – ZnSO4),
when heated in air, ZnO and SO2 are formed.
The atomic mass of zinc is 65, sulfur is 32.
Mass fraction of zinc – 65 / (65 + 32) * 100% = 67%.
Answer: 67% is a mass fraction of zinc in sulfide.

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