8. The standard enthalpy of formation of RbF (s) is - 557.7kJ/mol and the standard enthalpy of formation of RbF (aq, 1 m) is - 583.8 kJ/mol. Determine the enthalpy of solution of RbF and indicate whether the solution temperature will increase or decrease when RbF is dissolved in water.

Given

The enthalpy of formation of RbF (s) is - 557.7kJ/mol

The standard enthalpy of formation of RbF (aq, 1 m) is - 583.8 kJ/mol

The enthalpy of solution of RbF = Enthalpy of RbF (aq) - Enthalpy of formation of RbF (s)

= - 583.8 - (-557.7) kJ/mol

= - 26.1 kJ/mol

The enthalpy is negative which means that the temperature will rise when RbF is dissolved.