Chemistry
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Charges on the metal
MgSO4 = +2
NiSO4*6H2O = +2
CoCl2*6H2O = +2
KCr(SO4)2*12H2O = +3
CuSO4*5H2O = +2
(NH4)2Cr2O7 = +2
FeSO4*7H2O = +2
MnCl2*4H2O = +2
FeCl3*6H2O = +3

I'm not sure if the above answers are correct, could someone please check them over and let me know?

You missed two; Cr alum and (NH4)2Cr2O7.
KCr(SO4)2. I think they wanted BOTH K and Cr but those are not +3 anyway you stack it. K is +1, Cr is +3, and that balances the 2 each for sulfate for a total of 4.
For (NH4)2Cr2O7.
NH4 is +1 so two of them are +2.
O is 2 and seven of them are 14
Therefore, total Cr must be +12 (+12+2=14 which balances 14) so each Cr must be +6. 
wow, those ones are confusing...