Litmus paper is made from water-soluble dyes which are extracted from lichens. This paper is used as an acid-base indicator. Which of these common household substances would turn blue litmus paper red?
A common household substance that will turn blue litmus paper red would be lemons, apples, tomatoes, other citrus fruits (they contain citrus acid), vinegar, and vitamin C.
Blue litmus paper turn red in the presence of an acid, and vinegar is the only choice that is an acid. The rest of the choices are bases and blue litmus would stay blue when dipped in them.
