Question

15 points I. (5 points) Identify which of the following are due to intramolecular or intermolecular forces? A) Those preventing oil from evaporating at room temperature. B) Those preventing butter from melting in a refrigerator. C) Those allowing silver to tarnish. D) Those allowing fog to form on a cool, humid evening. E) Those responsible for the low boiling point of hexane.

Answer 1

A) The force that prevent oil from evaporating at room temperature is intermolecular forces. Oil are long chain of hydrocarbons. The cohesive forces responsible for its high boiling point are almost solely London dispersion froces between the hydrocarbon chains. Viscocity and surface tension also contributes to it.

B) Butter contain fatty acids. Fatty acids are carboxylic acids that are structural components of many lipids. They may be saturated or unsaturated. Intermolecular forces of attraction increases at low temperature thus prevent butter from melting.

C) The tarnishing the result of reaction silver and sulphur containing substance in the air. This is Intramolecular force of attraction.

D) The attraction between all gas molecules will cause them to form liquids or solids. This is due to intermolecular forces.  When gaseous water is cooled sufficiently, the attractions between H2O molecules will be capable of holding them together when they come into contact with each other; the gas condenses, forming liquid H2O.

E) Low boiling point of hexane

Boiling point depend upon the intermolecular forces of attraction. Vanderwalls forrce is present between the molecules of hexane. N-hexane has low B.P due to weak vander wall force of attraction.