## Chemistry and Chemical Reactivity (9th Edition)

Molar masses: $MgSO_4: 120.361\ g/mol,\ H_2O: 18.015\ g/mol$ Initially the number of moles: $2.465\ g = n \times (120.361+7\times18.015)g/mol$ $n=0.01\ mols$ After heating $1.744\ g = 0.01\ mol \times( 120.361 + k\times18.015)g/mol$ $k=3.0$ So the formula of the dehydrated salt is: $MgSO_4 (H_2O)_3$