Question

1)Which of the following would be expected to be the most soluble in water?

butanol
proanol
propane

2) Liquid hexanol (C₆H₁₃OH) has a normal boiling point of 158 °C and liquid decanol (C₁₀H₂₁OH) has a normal boiling point of 233 °C

(a) In which of the two are the intermolecular forces the strongest?

(b) Which of the two would you expect to have the lowest surface tension at 25 °C?

Answer 1

Intermolecular forces:

Intermolecular forces are the forces that act between one molecule to other molecules as attraction. These are mainly three types:

1. Dipole-dipole interaction
2. Hydrogen bond
3. London dispersion force.

London dispersion force:

1. London dispersion force is an intermolecular force which occurs between an atoms or molecules which are polar or non-polar and another atom or molecule which are polar or non-polar.
2. It occurs between all molecules or atom.
3. London dispersion forces are the result of temporary dipoles in the atoms or molecules.

Dipole-dipole interaction:

1. This type of interaction forces is found between polar molecules.
2. The strength of this force is increasing with increasing polarity of molecules.

Hydrogen bond:

1. Generally hydrogen bond is found in those molecules which have covalently hydrogen atom bonded with high electronegative atoms like oxygen, nitrogen and fluorine.
2. Hydrogen bond found in polar molecules containing unpaired electrons along with a hydrogen atom bonded with oxygen, nitrogen or fluorine atom

   1)Which of the following would be expected to be the most soluble in water?

   butanol
   proanol
   propane

   Alcohols are soluble in water due to formation of H bond. Thus butanol and propanol are soluble in water, but the solubility of alcohols in water are decreases as number of carbon atoms increases. Thus propanol is most soluble in water.

   2) Liquid hexanol (C₆H₁₃OH) has a normal boiling point of 158 °C and liquid decanol (C₁₀H₂₁OH) has a normal boiling point of 233 °C

   (a) In which of the two are the intermolecular forces the strongest?

   Liquid hexanol (C₆H₁₃OH) has a normal boiling point of 158 °C and liquid decanol (C₁₀H₂₁OH) has a normal boiling point of 233 °C

   Therefore decanol has stronger intermolecular forces means higher boiling point than the Liquid hexanol .

   (b) Which of the two would you expect to have the lowest surface tension at 25 °C?

   Surface tension depends on both the temperature and the intermolecular forces of the substance. At any given temperature, the substance with stronger intermolecular forces has higher surface tension. Thus Liquid hexanol (C₆H₁₃OH) has the lowest surface tension at 25 °C