## Chemistry and Chemical Reactivity (9th Edition)

Number of moles of magnesium sulfate: $0.824\ g\div 120.36\ g/mol=0.00685\ mol$ Number of moles of water: $(1.687-0.824)\ g\div18.015\ g/mol=0.04790\ mol$ Ratio: $0.04790/0.00685=7.00$ 7 molecules of water per formula unit.