Q.Which of the following compound is used as an anti-freeze in automobile radiator ?

Ethane-1,2-diol (ethylene glycol), a dihydric alcohol, is completely miscible with water and lowers the freezing point of the radiator coolant mixture substantially, making it the standard automotive anti-freeze.

An effective anti-freeze must be fully miscible with water, chemically stable, non-volatile (high boiling point, so it doesn't evaporate from a hot engine), and must significantly depress the freezing point of the water-antifreeze mixture (a colligative, freezing-point-depression effect). Ethane-1,2-diol, $HOCH_2CH_2OH$, satisfies all these requirements and is the compound universally used (typically ~30-50% by volume in water) in automobile radiators to prevent the coolant from freezing in cold climates and to raise its boiling point in hot conditions. Methanol and ethanol are far more volatile (low boilin …