Question

Methanol ---> Normal BP: 64.6°C --> dHvap: 35.3kJ/mol

iso-Propanol ---> Normal BP: 82.3°C --> dHvap: 45.4kJ/mol

Cyclohexane ---> Normal BP: 80.7°C --> dHvap: 33.1kJ/mol

Question: Ethanol has a normal BP of 78.3°C. Why is the normal BP higher than methanol but lower than iso-propanol listed above? Would you expect the heat of vaporization of ethanol to follow the same trend? Explain.

Answer 1

molar mass CH3OH = 32
molar mass ethanol = 46
molar mass isopropanol = 60
longer chains, more complicated molecules, high intermolecular forces. I would expect enthalpy vap to follow the same trend.

Answer 2

Thank you so much :)