Asked by Lena
I don't understand how to find the formula of a hydrate. Here's one of the question. if you guide me through it I think I'll be able to do the rest of them. Thanks :)
When 100g of ZnSO4xœH2O is heated, 43.86g of water is given off. Calculate the formula of the hydrate.
When 100g of ZnSO4xœH2O is heated, 43.86g of water is given off. Calculate the formula of the hydrate.
Answers
Answered by
Jen
ZnSO4xH20 ¨ ZnSO4 + xH2O
No. of moles of H2O = mass € molar mass
= 43.86 € 18
= 2.4367 mols
No. of moles of ZnSO4xH20
= mass € molar mass
= 100 € (161 + 18x) mols
No. of moles of ZnSO4xH20
= 1/x X no. of moles of H2O
= 1/x X 2.4367
= i.e. 2.4367/x mols
Therefore, 2.4367/x = 100 € (161 + 18x)
Solving the equation,
100x = 2.4367 (161+18x)
56.1394x = 392.3087
x = 6.990
= 7 (whole no.)
Hence the formula is ZnSO4. 7H2O
There are 7 water molecules.
Answered by
Jen
Please note that those missing symbols mean divide. i.e.
no. of moles = mass/molar mass
no. of moles = mass/molar mass
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