1.615 g of anhydrous ZnSO4 was places in moist air. After a few days, its mass was found to be 2.875g. The molecular formula for hydrated zinc sulphate is
A
ZnSO4.2H2O
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B
ZnSO4.5H2O
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C
ZnSO4.7H2O
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D
ZnSO4.10H2O
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Solution
The correct option is CZnSO4.7H2O Molecular mass of anhydrous ZnSO4=65.5+32+(4×16)=161.5
1.615 g of anhydrous ZnSO4 combines with (2.875 - 1.615) g = 1.260 g of water
Hence 161.5 g of ZnSO4 combines with 126 g of water = 12618=7 moles of water
Hence formula of hydrate ZnSO4 is ZnSO4.7H2O