Which of the following alkanes has the highest boiling point?
Ans. A All the given choices are alkanes. Item I is an unbranched alkane. Items II, III, IV have increasing degrees of branching. Branching decreases the area of contact and thereby decreases the intermolecular interactions. So the unbranched alkane has the highest boiling point. Keep in mind that without actually measuring the properties, we can only compare compounds of comparable weights and number of carbons with reasonable accuracy.