Question

Bromine melts at -7.25 degree C and boils at 58.8 degree C. The enthalpy of fusion of bromine is 10.57 kJ/mol and the enthalpy of vaporization of bromine is 29.96 kJ/mol. The specific heat of liquid bromine is 0.474 J/g∙K. How much heat, in kJ, is required to convert 25.0 g of solid bromine at -7.25 degree C to the gas phase at 58.8 degree C?

Answer 1

From solid at the start to the melting point, heat required is
q1 = mass x specific heat solid x (Tfinal-Tinitial)

At the melting point, q for melting is
q2 = mass solid x heat fusion

From the melting point to the boiling point, q for heating the liquid phase is
q3 = mass x specific heat x (Tfinal-Tinitial)

At the boiling point, the heat to convert to vapor is
q4 = mass liquid x heat vaporization

Total heat is q1 + q2 + q3 + q4.