Question

why in cold countries ice on roads are melted by sprinkling solid calcium chloride rather than sodium chloride ?

Answer 1

When some soluble salt is added to water, it decreases freezing point of water, it is called depression in freezing point. In simple terms, it doesn't let the water freeze easily. When salt is sprinkled over ice, it's freezing point is lowered up to -20°C, ice is cleared off.