Which of the following statements is/are correct? I. Melting point of alkane increases with increase in number of C atoms and with increase in branching. II. Boiling point of alkane increases with increase in number of C atoms but with decrease in branching. III. Cycloalkanes have lower boiling point than normal alkane with same number of C atoms. IV. Alkenes have lower boiling point than same number of C atoms in alkanes.

Question

Which of the following statements is/are correct? I. Melting point of alkane increases with increase in number of C atoms and with increase in branching. II. Boiling point of alkane increases with increase in number of C atoms but with decrease in branching. III. Cycloalkanes have lower boiling point than normal alkane with same number of C atoms. IV. Alkenes have lower boiling point than same number of C atoms in alkanes. (A) (I), (II) (B) (I), (II), (III) (C) (III), (IV) (D) (IV)

Tardigrade Admin · Accepted Answer

Higher the intermolecular forces higher is the boiling point because as the surface area increases the Van der wall force of attraction increases.
Melting point depends on packing fraction, more branching, surface area of molecules decreases, and they become more compact and thus easier to pack hence, melting point increases.