Which property distinguishes a carboxylic acid from other organic compounds in litmus tests?

Carboxylic acids are known for their acidic properties, which stem from their ability to donate a proton (H⁺) in aqueous solutions. This specific characteristic is what makes them distinguishable from other organic compounds during a litmus test. When a carboxylic acid is tested with litmus paper, it donates a proton to water, leading to the formation of hydronium ions (H₃O⁺). The presence of these ions causes the pH of the solution to drop, resulting in a color change on the litmus paper.

In this case, a carboxylic acid will turn blue litmus paper red, which is indicative of an acidic environment created by the release of protons. This response is a clear sign of the acid-base behavior of carboxylic acids and serves as a reliable method to identify their presence among a variety of organic compounds.

Other responses do not accurately reflect the acidic nature of carboxylic acids. For instance, turning red litmus blue is characteristic of basic substances, and no color change suggests a neutral solution, which does not apply to carboxylic acids. The idea of yellow litmus turning green does not align with standard litmus testing procedures. Overall