Chloride ions show which observation when damp litmus paper is used?

• A. Bleaches damp litmus paper
• B. Litmus paper turns blue
• C. Litmus paper turns red
• D. No change

Answer: (A)

Chloride ions by themselves don’t change litmus, but they can produce chlorine gas when a strong oxidizing acid like concentrated sulfuric acid is added. The chloride is oxidized to Cl2, and the chlorine gas bleaches damp litmus paper, so blue litmus loses color (turns white). This bleaching effect is the key observation.