A sample of a solution with a pH of 10 is tested separately with phenolphthalein and litmus. The colors of the indicators are as follows:

A sample of a solution with a pH of 10 is tested separately with phenolphthalein and litmus. The colors of the indicators are as follows:

• A. litmus is blue; phenolphthalein is pink
• B. litmus is red; phenolphthalein is pink
• C. litmus is blue; phenolphthalein is colorless
• D. litmus is red; phenolphthalein is colorless

Answer: (A)

Basic solutions turn litmus blue, and phenolphthalein changes from colorless to pink as the solution becomes basic. A pH of 10 indicates a strong base, so litmus will be blue. Phenolphthalein is colorless in acidic/neutral solutions but turns pink in basic conditions, especially at higher pH, so it will be pink. This combination matches a basic solution, making blue litmus and pink phenolphthalein the correct colors.

Basic solutions turn litmus blue, and phenolphthalein changes from colorless to pink as the solution becomes basic. A pH of 10 indicates a strong base, so litmus will be blue. Phenolphthalein is colorless in acidic/neutral solutions but turns pink in basic conditions, especially at higher pH, so it will be pink. This combination matches a basic solution, making blue litmus and pink phenolphthalein the correct colors.