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.

The answer is D) It should turn the methyl orange to red because it is an acid

The answer is: It should turn methyl orange to red because it is an acid.

This compound is acid.

Bases turn red litmus paper blue and acids turn blue litmus paper red.

Acid-base indicators are usually weak acids or bases and they are chemical detectors for hydrogen or hydronium cations.

Example for acid-base indicator is phenolphthalein (molecular formula C₂₀H₁₄O₄). Phenolphthalein is colorless in acidic solutions and pink in basic solutions.

Another example is methyl orange. It is red colour in acidic solutions and yellow colour in basic solutions.