Experiment help

[andy456]

Okay so in class we are determining the number of moles of H2O in hydrated CuSO4; CuSO4.xH2O
We heated the copper sulfate till it reached a constant mass.
Original mass of crucible (with powder): 21.939g
End weight of crucible (with powder):   20.330g
Therefore, the mass of water lost is 1.609g

Then n(H2O)= 1.609/18
                 = 0.0274mol
                 =0.03mol
n(CuSO4)= 4.38/159.7
             =0.0894mol
             =0.09mol

Therefore, 0.09/0.03 = 3
CuSO4.3H2O
*I thought it was meant to be 5

Im stuck on these questions we have to answer.

1.Would you expect copper flouride to have a larger or smaller number of water molecules attracted to it than copper chloride? Why?

2. Two errors that lead to number of molecules lower than the real value.

3. An error that could lead to the number of water molecules higher than the real value

4. If this experiment was done with copper carbonate why would it reveal a negative number of water molecules.

Thanks to anyone that helps in advance.