Car and truck engine coolants contain mixtures of water and the high-boiling, non-electrolyte ethylene glycol or propylene glycol. As coolants, the use of the mixtures of these non-electrolytes are superior to the use of pure water.
H-O-H
HO-CH2-CH2-OH
HO-CH2-CH2-CH-OH
Water
ethylene glycol
propylene glycol
Using predominant intramolecular forces, explain why the mixture has a higher boiling point than that of water.
The higher boiling point of the mixture compared to pure water can be attributed to the presence of ethylene glycol or propylene glycol in the coolant mixture. These non-electrolytes have stronger intermolecular forces (specifically hydrogen bonding) than water molecules.
In water, the predominant intermolecular force is hydrogen bonding between the water molecules. However, in ethylene glycol and propylene glycol, there are additional intermolecular forces such as dipole-dipole interactions and hydrogen bonding between the hydroxyl groups on the molecules. These additional intermolecular forces make it more difficult for the molecules to overcome the attractive forces and vaporize, resulting in a higher boiling point for the coolant mixture compared to water.
Therefore, the mixture of ethylene glycol or propylene glycol with water has a higher boiling point due to the stronger intermolecular forces present, making it more effective as a coolant for car and truck engines.