Mole calculation!!!

Torch

2011-03-25 2:16 am

A hydrated salt of copper contains 63.9% by mass of the anhydrous salt. The anhydrous salt has the following percentage composition by mass: copper 39.8%, sulphur 20.1%, oxygen 40.1%
Find the empirical formula of the hydrated salt.
(relative atomic mass: H=1.0 O=16.0, S=32.1, Cl=35.5, Ca 40.1, Cu= 63.5)

回答 (1)

知識就是力量

2011-03-25 4:46 am

✔ 最佳答案

Suppose the mass of copper, sulphur and oxygen are 39.8g, 20.1g and 40.1g respectively
mole of Cu : mole of S : mole of O
= 39.8/63.5 : 20.1/32.1 : 40.1/16
= 0.6268 : 0.6262 : 2.50625
= 1:1:4
So empirical formula of the anhydrous salt: CuSO4
Let the empirical formula of the hydrated salt be CuSO4 . xH2O
Suppose the mass of CuSO4 and H2O are 63.9g and 36.1g
mole of CuSO4 : mole of H2O
= 63.9/159.6 : 36.1/18
= 0.4004 : 2.006
= 1:5
Empirical formula of the hydrated salt: CuSO4 . 5H2O

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