Question

Arrange the following in decreasing order of their boiling points:
(1) n-butane
(2) $2$-methyl butane
(3) n-pentane
(4) $2,2$-dimethyl propane

• A. 1>2>3>4
• B. 2>3>4>1
• C. 4>3>2>1
• D. 3>2>4>1

Answer 1

The correct option is D 3>2>4>1

Boiling point is directly proportional to molar mass and surface area . It decreases on branching because surface area decreases. Hence , n-pentane has the highest and n-butane has the lowest boiling points and in rest two branching is there , therefore $2$-methyl butane has higher boiling point than $2,2$-dimethylpropane.

Hence, Option "D" is the correct answer.