Question 11.5.1: Predict physical properties using relative polarizability. C......
Predict physical properties using relative polarizability.
Consider the two alcohols methanol (CH_{3}OH) and 1-hexanol (C_{6}H_{13}OH).
a. Which alcohol has the higher boiling point?
b. Which has the lower enthalpy of vaporization?
c. What type of IMF is primarily responsible for the differences in the physical properties of these alcohols?
You are asked to predict the relative boiling point and enthalpy of vaporization for two alcohols and to identify the IMF primarily responsible for the differences in the physical properties of the alcohols.
You are given the chemical formulas of the alcohols.
Both alcohols can form hydrogen bonds, but they differ in their molar masses (CH_{3}OH, 32.0 g/mol; C_{6}H_{13}OH, 102 g/mol).
a. The alcohol with the higher molar mass has stronger IMFs and therefore a higher boiling point.
CH_{3}OH, 65 °C; C_{6}H_{13}OH, 158 °C
b. The alcohol with the lower molar mass has weaker IMFs and therefore a lower enthalpy of vaporization.
CH_{3}OH, 35.2 kJ/mol; C_{6}H_{13}OH, 44.5 kJ/mol
c. Dispersion forces (induced dipole–induced dipole) IMFs are primarily responsible for the differences in boiling point and enthalpy of vaporization for these two alcohols.