Which of the following is a typical property of a base (in aqueous solution)?

• A. It has a pH greater than $7$.
• B. It increases the concentration of $H_3{O}^{+}$ in water.
• C. It reacts with metals to produce $H_2$ gas as its defining property.
• D. It turns blue litmus paper red.

Answer: (A)

Verified step by step guidance

1. Recall the definition of a base in aqueous solution: a base is a substance that increases the concentration of hydroxide ions (OH\textsuperscript{-}) when dissolved in water.
2. Understand that pH is a measure of the acidity or basicity of a solution, where pH less than 7 indicates acidic, pH equal to 7 is neutral, and pH greater than 7 indicates basic (alkaline) solution.
3. Recognize that a typical property of a base is that it has a pH greater than 7, meaning it decreases the concentration of hydronium ions (H\textsubscript{3}O\textsuperscript{+}) and increases OH\textsuperscript{-} concentration.
4. Note that increasing the concentration of H\textsubscript{3}O\textsuperscript{+} ions is a property of acids, not bases.
5. Remember that bases do not typically react with metals to produce hydrogen gas as a defining property, and they turn red litmus paper blue, not blue litmus paper red.