What color does lead acetate paper turn when hydrogen sulfide gas is present?

Lead acetate paper is specifically designed to detect the presence of hydrogen sulfide (H₂S) gas in an environment. When hydrogen sulfide is present, it reacts with lead acetate on the paper, causing it to undergo a chemical change. This reaction results in the formation of lead sulfide, which gives the paper a distinct brown coloration. The ability of lead acetate paper to turn brown is a practical indicator used in various industrial and safety applications to signal the presence of this hazardous gas.

In contrast, the other color options do not accurately represent the outcome of this specific chemical reaction. Understanding how this detection method operates is crucial for ensuring safety in environments where hydrogen sulfide is a risk, such as in mining and industrial settings.