Which gas turns lime water milky due to the formation of an insoluble white precipitate of calcium carbonate when bubbled through it?

💡 Solution & Explanation

Passing carbon dioxide gas through an aqueous solution of calcium hydroxide, known as lime water, turns the solution milky because of the precipitation of insoluble calcium carbonate. Continuing to pass carbon dioxide redissolves the precipitate into soluble calcium bicarbonate. Sulfur dioxide also causes milkiness by forming calcium sulfite, but carbon dioxide is the standard laboratory test reagent.