Answer
2
Work Step by Step
Molar masses (g/mol): $MgSO_4: 120.37g/mol,\ H_2O:18.02,\ MgSO_4\dot{}7\ H_2O: 246.47$
Mass of epsom salt: 1.394g
Mass of the product: 0.885g
Mass of lost water 1.394- 0.885= 0.509g
Number of moles:
$MgSO_4\dot{}7\ H_2O$: $1.394/246.47=5.66\times10^{-3}\ mol$
lost $H_2O$: $0.509/18.02=0.0282\ mol$
Ratio of the number of moles of lost $H_2O$ by $MgSO_4\dot{}7\ H_2O$:
$0.0282\div5.66\times10^{-3} = 4.99$
5 moles of hydration water are lost per mole of epsom salt:
Final molecular formula: $MgSO_4\dot{}2\ H_2O$
The value of x is 2.
