Hess's law can be used to derive the following mathematical equation for determining the heat of reaction for a chemical reaction given heat of formation data.
Use Hess's law or the above equation to find the heat of solution when potassium sulfate is dissolved in water.
K2SO4 (s) → 2 K+ (aq) + SO42- (aq) = ?
K (s) → K+ (aq) = -252 kJ
S (s, rhombic) + 2 O2 (g) → SO42- (aq) = -909 kJ
2 K (s) + S (s) + 2 O2 (g) → K2SO4 (s) = -1438 kJ