Question

What will be the action of the following substances on red and blue litmus paper?

• Dry HCl gas
• Moistened ${\text{NH}}_3$ gas
• Lemon juice
• Carbonated soft drink
• Curd
• Soap solution.

Answer 1

Effects on litmus papers:

• Dry HCl gas: No change on litmus paper
• Moistened ${\text{NH}}_3$ gas (basic): Red litmus will turn blue.
• Lemon Juice (contains citric acid): Blue litmus will turn red.
• Carbonated soft drinks (contains carbonic acid): Blue litmus will turn red.
• Curd (contains lactic acid): Blue litmus will turn red.
• Soap solution (basic): Red litmus will turn blue.