Final answer:
Yes, a reaction is occurring when using litmus paper. Blue litmus paper turns red in the presence of an acidic solution, while red litmus paper turns blue in the presence of a basic solution.
Step-by-step explanation:
Yes, a reaction is occurring when using litmus paper. Litmus paper is a pH indicator that changes color in the presence of acidic or basic substances. When an acidic solution comes into contact with blue litmus paper, it turns the paper red. On the other hand, when a basic solution comes into contact with red litmus paper, it turns the paper blue.