Question

An unknown substance turns blue litmus paper to red. Which additional test could be used to confirm the substance’s identity?
It should turn phenolphthalein from colorless to pink because it is a base.
It should turn phenolphthalein from pink to colorless because it is a base.
It should turn methyl orange to orange because it is an acid.
It should turn methyl orange to red because it is an acid.

Answer 1

"It should turn methyl orange to red because it is an acid."

Reason: turning blue litmus red indicates an acidic substance. Methyl orange is red in acidic solution (orange in neutral/weakly basic), whereas phenolphthalein is colorless in acid and only pink in basic solutions.