Which of the following is a characteristic property of an acid in aqueous solution?

• A. It increases the concentration of $O{H}^{-}$ (hydroxide) ions.
• B. It has a $pH>7$ at room temperature.
• C. It increases the concentration of $H_{3}O+$ (hydronium) ions.
• D. It turns blue litmus paper blue.

Answer: (C)

Verified step by step guidance

1. Recall the definition of an acid according to the Arrhenius theory: an acid increases the concentration of hydrogen ions (H\_3O\^+) in aqueous solution.
2. Understand that hydroxide ions (OH\^-) are characteristic of bases, not acids, so an acid does not increase OH\^- concentration.
3. Recognize that acids typically have a pH less than 7 at room temperature, so a pH greater than 7 is not a property of acids.
4. Know that acids turn blue litmus paper red, not blue, so turning blue litmus paper blue is a property of bases.
5. Therefore, the characteristic property of an acid in aqueous solution is that it increases the concentration of hydronium ions (H\_3O\^+).