In the Brønsted–Lowry definition, what is an acid?

• A. A substance that produces hydroxide ions ($O^{H_{-}}$) when dissolved in water
• B. A substance that is always neutral in aqueous solution
• C. A substance that donates a proton ($H^{+}$) to another species
• D. A substance that accepts a proton ($H^{+}$) from another species

Answer: (C)

Verified step by step guidance

1. Recall the Brønsted–Lowry acid-base theory, which defines acids and bases based on proton transfer.
2. Understand that in this theory, an acid is a species that donates a proton (H\textsuperscript{+}) to another species during a chemical reaction.
3. Recognize that a base, conversely, is a species that accepts a proton (H\textsuperscript{+}) from another species.
4. Note that producing hydroxide ions (OH\textsuperscript{-}) in water is characteristic of bases, not acids, according to this definition.
5. Therefore, the correct identification of an acid in the Brønsted–Lowry sense is a substance that donates a proton (H\textsuperscript{+}) to another species.