The correct answer is option 3: White.
When carbon dioxide (CO2) gas is passed through lime water (calcium hydroxide solution), a chemical reaction occurs. The reaction produces a precipitate, which is a solid substance that forms when two different chemicals react in a solution.
In this reaction, carbon dioxide reacts with calcium hydroxide to form calcium carbonate, which is a white solid. Therefore, when CO2 gas is passed through lime water, a white precipitate of calcium carbonate is obtained.
It is important to note that the color of the precipitate can vary depending on the concentration and impurities present in the lime water. However, the most common and expected color of the precipitate is white.
In summary, passing carbon dioxide gas through lime water results in the formation of a white precipitate of calcium carbonate.