Understanding the Relationship Between Carbon Chain Length and Boiling Point in Alkanes

As the number of carbon atoms in a molecule in any homologous series increases, the boiling point (a)________________The boiling point of straight-chain alkanes (b)________________when a methylene (-CH2-) group is added, because the strength of the London forces between molecules increases as the relative molecular mass (number of electrons in the molecule) of the alkanes (c)______________. A similar trend is seen in the boiling points of other homologous series.

(a)increases(b)increases(c)increases

(a) As the number of carbon atoms in a molecule in any homologous series increases, the boiling point also increases. This is because as the size and mass of the molecule increase, there are more points of contact between the molecules, and therefore more intermolecular forces require more energy to break, resulting in a higher boiling point.

(b) The boiling point of straight-chain alkanes generally increases with increasing chain length. This is because longer chains have more surface area and more points of contact, which leads to stronger London dispersion forces. The strength of these forces increases with the size and mass of the molecule, resulting in a higher boiling point.

(c) The boiling point of alkanes increases with the relative molecular mass of the molecule because the increased number of electrons in the molecule creates stronger London dispersion forces. This occurs because with a larger molecular mass, there are more electrons which lead to stronger attractive forces between the molecules. Therefore, the boiling point increases as the number of carbon atoms in the molecule increases.

More Answers: