Question

The molar heats of fusion and vaporization of ethanol are 7.61 and 26.0 kJ/mol, respectively. Calculate the molar entropy changes for the solid-liquid and liquid-vapor transitions for ethanol. At 1 atm pressure, ethanol melts at −117.3°C and boils at 78.3°C.

Answer 1

ΔS°fus = 48.88 J/K*mol

ΔS°vap =74.01 J/K*mol

Step-by-step explanation:

Step 1: Data given

The molar heats of fusion of ethanol = 7.61 kJ/mol = 7610 J/mol

The molar heats of vaporization of ethanol = 26.0 kJ/mol = 26000 J/mol

Pressure = 1 atm

Ethanol melts at −117.3°C and boils at 78.3°C.

Step 2: Calculate the molar entropy changes for the solid-liquid and liquid-vapor transitions for ethanol.

ΔS°fus = 7610 / (273−117.3)

ΔS°fus = 48.88 J/K*mol

ΔS°vap = 26000/(273+78.3)

ΔS°vap =74.01 J/K*mol