When carbon dioxide is passed through lime water, it first turns milky and then turns colourless.

Ans.

1. When carbon dioxide is passed through lime water, initially white insoluble calcium carbonate is formed. Hence lime water turns milky.

When carbon dioxide is passed through lime water for a longer time, it reacts with calcium carbonate to form colourless, water soluble calcium bicarbonate. Hence, the lime water turns colourless.