Question

A substance containing hydrogen and releasing $\text{H}^+$ in aqueous medium is acid. Identify theory suggesting this concept, from following.

• A. Ostwald theory
• B. Bronsted-Lowry theory
• C. Arrhenius theory
• D. Lewis theory

Hint:

The keyword "aqueous medium" is your definitive clue here. Arrhenius's model is uniquely limited to and dependent on water chemistry, whereas subsequent theories expanded to encompass non-aqueous systems and generalized electronic behavior.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks to identify the historical chemical definition or theory that defines an acid specifically as a hydrogen-containing compound that dissociates to release free hydrogen ions ($\text{H}^+$) when dissolved in an aqueous water medium.

Step 2: Detailed Explanation:
Let's examine the foundational definitions of acids across the prominent chemical frameworks:

Arrhenius Theory (1887): Posits that an acid is a hydrogen-bearing substance that undergoes electrolytic dissociation in water to yield hydrogen ions ($\text{H}^+$), whereas a base yields hydroxyl ions ($\text{OH}^-$). This definition completely matches the criteria stated in the prompt.

Brønsted-Lowry Theory (1923): Expands the framework by defining an acid more broadly as a proton ($\text{H}^+$) donor, independent of whether the solvent environment is aqueous.

Lewis Theory (1923): Abandons proton tracking entirely to classify an acid as an electron-pair acceptor.
Therefore, the requirement of an aqueous medium is an explicit constraint of the Arrhenius framework.

Step 3: Final Answer:
The theory suggesting this concept is the Arrhenius theory, corresponding to option (C).