Answer to Question #96602 in Inorganic Chemistry for Agou alier

Question

The boiling points of the isomers of C5H12 are
B Pt (K)
pentane 309.2
2-methylbutane 301.0
2,2-dimethylpropane 282.6
a) What are the forces attracting pentane molecules to their neighbours in liquid
pentane?
b) Explain why the boiling point becomes lower as the isomer becomes more
branched

Answer 1

Solution.

A)

Van der Waals forces act between pentane molecules. These are very weak forces between molecules.

B)

The boiling point of alkanes depends on the molecular weight of the hydrocarbon. The greater the number of carbon atoms, the higher the boiling point. But the boiling point of branched hydrocarbons is lower than that of hydrocarbons of normal structure. This is due to the fact that branched molecules have less dense packaging and intermolecular forces of attraction are weaker.

Answer:

A)

Van der Waals forces act between pentane molecules. These are very weak forces between molecules.

B)

The boiling point of alkanes depends on the molecular weight of the hydrocarbon. The greater the number of carbon atoms, the higher the boiling point. But the boiling point of branched hydrocarbons is lower than that of hydrocarbons of normal structure. This is due to the fact that branched molecules have less dense packaging and intermolecular forces of attraction are weaker.