Why do solid alkanes have low melting point?
Why do solid alkanes have low melting point?
The correct option is B Strong repulsive forces between electrons of neighbouring atoms
This question requires you to think in terms of what kind of forces are holding together the molecules in a solid! Since solid alkanes are easy to melt, it points to the strong repulsive forces between electrons of neighbouring atoms. Let us explore this in more detail:
Solid alkanes are soft and have low melting points because of the weak intermolecular forces between the alkane molecules. This is very different from molecules in ice, where the molecules are connected by stronger hydrogen bonds. Comparatively, van der Waals are weaker in say - solid methane.
Methane's molar mass is just around 16 g/mol whereas water's molar mass is 18 g/mol. But the melting point of methane is -182∘C whereas the melting point of water is 0∘ C. This is simply because of the greater intermolecular forces in water due to hydrogen bonding.
Strong repulsive forces between electrons of neighbouring atoms
This question requires you to think in terms of what kind of forces are holding together the molecules in a solid! Since solid alkanes are easy to melt, it points to the strong repulsive forces between electrons of neighbouring atoms. Let us explore this in more detail:
Solid alkanes are soft and have low melting points because of the weak intermolecular forces between the alkane molecules. This is very different from molecules in ice, where the molecules are connected by stronger hydrogen bonds. Comparatively, van der Waals are weaker in say - solid methane.
Methane's molar mass is just around 16 g/mol whereas water's molar mass is 18 g/mol. But the melting point of methane is -182∘C whereas the melting point of water is 0∘ C. This is simply because of the greater intermolecular forces in water due to hydrogen bonding.
