Hi,
So in my Chemistry class, we did an experiment for finding the formula of Hydrated Copper (II) Sulphate. Basically, in CuSO4.xH2O, we have to find out the value of 'x'. We started out with Hydrated Copper Sulphate, which was blue, and we heated it until it turned white and most of the water had evaporated. The teacher gave us the steps listed below, and I did them many times and always got the same answer, but my teacher told me it was wrong. Here are the steps, please tell me where I went wrong:
a) Mass of crucible: 122.91g
b.) Mass of crucible + Blue Copper (II) Sulphate: 124.29g
c.) Mass of crucible + white Copper (II) Sulphate: 123.28g
d.) Mass of blue copper sulphate (step b - step a): 1.38g
e.) Mass of white copper sulphate (step c - step a): 0.37g
f.) Mass of water (step d - step e): 1.01g
g.) Moles of white Copper (II) Sulphate (step e / Mr of CuSO4): 0.0023 moles
h.) Moles of Water (step f / Mr of H2O): 0.056
i.) Moles of Water / Moles of Copper (II) Sulphate (step h / step g): 24.3
j.) Formula of Hydrated Copper (II) Sulphate: CuSO4.24H2O
Note: Obviously, steps a,b, and c were attained through weighing, not through calculation.
All seems right for me, but my teacher assured me that it has to be a much smaller number, around 5 (but possibly a little higher or lower due to mistakes in the experiment). But it definitely can't be 24. Please help me find the correct answer by telling me where I went wrong!
Thank you.