Question

How many tons of Zn can be obtained from 10 tons of ZnS, assuming that the yield is 75%? (Zn=65.3 and S=32)
1. 5
2. 10
3. 12
4. 15

Answer 1

Hint: ZnS is generally an inorganic compound known by the name zinc sulfide and it is the main form of zinc present in nature and generally occurs from the mineral sphalerite which is usually black in color but after purification ZnS is found as a pure white compound which is used as a pigment.

Complete Step by step solution: Zinc sulfide is generally transparent in nature so it is used in making windows for visible and infrared optics. It mainly exists into main crystalline forms and in each form coordination of Zn and S is tetrahedral. The more stable cubic form is known as zinc blende while the hexagonal is known by the name wurtzite. Reaction of zinc sulfide can be shown as:
$ZnS+{{O}_{2}}\to Zn+S{{O}_{2}}$
1 mole of ZnS = 97 g and
1 mole of Zn = 65 g
Hence we can say that
97g of ZnS gives 65g of Zn
$\therefore $1g of ZnS gives $\dfrac{65}{97}$g of Zn
So 10 tons of ZnS gives $\dfrac{65}{97}\times 10$tons of Zn = 6.7 ton
According to question yield is 75%
So the yield can be calculated as: $\dfrac{75}{100}\times 6.7$= 5.025 tons

Hence we can say that option 1 is the correct answer.

Note: Zinc sulfide is generally produced from waste materials from other applications. Main sources of zinc sulfide are smelter, slag and pickle liquors. It is also used as a by-product for the synthesis of ammonia from methane where zinc oxide is used to scavenge hydrogen sulfide impurities in the natural gas.