Among the following reagents, salt solution, sodium hydroxide solution and dilute sulfuric acid can be identified as () A dilute hydrochloric acid B colorless phenolphthalein C litmus test solution D limestone Why?

Among the following reagents, salt solution, sodium hydroxide solution and dilute sulfuric acid can be identified as () A dilute hydrochloric acid B colorless phenolphthalein C litmus test solution D limestone Why?

C. The litmus test solution turns red with acid and turns blue with alkali. The sodium hydroxide solution is alkali and turns blue. The dilute sulfuric acid is acid and turns red. The salt solution salt does not change color.

Color change of acid-base indicator and litmus phenolphthalein

Commonly used: methyl orange, phenolphthalein, litmus
Litmus turns red with acid and blue with alkali. Ph is purple from 8 to 10
Phenolphthalein does not change color with acid, weak alkali pink, strong alkali red