Which characteristic best identifies an Arrhenius base in aqueous solution?

• A. It donates a proton to another substance.
• B. It increases the concentration of $O^H-$ ions in water.
• C. It increases the concentration of $H^{}+$ ions in water.
• D. It accepts an electron pair to form a covalent bond.

Answer: (B)

Verified step by step guidance

1. Recall the Arrhenius definition of acids and bases: An Arrhenius acid increases the concentration of hydrogen ions (H\^+) in aqueous solution, while an Arrhenius base increases the concentration of hydroxide ions (OH\^-) in aqueous solution.
2. Identify the key ion associated with an Arrhenius base, which is the hydroxide ion (OH\^-). This ion is produced when the base dissociates or reacts in water.
3. Analyze each option in the problem: donating a proton corresponds to a Brønsted-Lowry acid, increasing H\^+ concentration corresponds to an Arrhenius acid, and accepting an electron pair corresponds to a Lewis base.
4. Recognize that the correct characteristic of an Arrhenius base is the increase in hydroxide ion concentration in water, which directly relates to the Arrhenius definition.
5. Conclude that the best identifying characteristic of an Arrhenius base in aqueous solution is that it increases the concentration of OH\^- ions in water.