'Stability of a crystal is reflected in the magnitude of its melting points', Comment. Collect melting points of solid water, ethyl alcohol, diethyl ether and methane from a data book. What can you say about the intermolecular forces between these molecules?
'Stability of a crystal is reflected in the magnitude of its melting points', Comment. Collect melting points of solid water, ethyl alcohol, diethyl ether and methane from a data book. What can you say about the intermolecular forces between these molecules?
(i) Stability of a crystal depends upon the magnitude of force of attraction between the constituent particles. Greater the attraction force, more will be the stability of the crystal. Hence, the melting point of the solid will be higher.
(ii) The melting point of different substances are :
(a) Water = 273 K
(b) Ethyl alcohol =155.7K
(c) Diethyl ether = 156.8 K
(d) Methane = 90.5 K
The intermolecular forces in molecules of water and ethyl alcohol are mainly hydrogen bonding. The magnitude is more in water than in ethyl alcohol which is evident from the values of their melting point. The force in the molecules of diethyl ether are dipolar forces while in methane, only weak van der Waals' forces of attraction exist. The values of melting point are the evidences for the same.
(i) Stability of a crystal depends upon the magnitude of force of attraction between the constituent particles. Greater the attraction force, more will be the stability of the crystal. Hence, the melting point of the solid will be higher.
(ii) The melting point of different substances are :
(a) Water = 273 K
(b) Ethyl alcohol =155.7K
(c) Diethyl ether = 156.8 K
(d) Methane = 90.5 K
The intermolecular forces in molecules of water and ethyl alcohol are mainly hydrogen bonding. The magnitude is more in water than in ethyl alcohol which is evident from the values of their melting point. The force in the molecules of diethyl ether are dipolar forces while in methane, only weak van der Waals' forces of attraction exist. The values of melting point are the evidences for the same.
