Step 1: Understanding the Question:
The question asks to identify an Arrhenius base from a list of chemicals based on the specific definition provided by Arrhenius theory.
Step 2: Detailed Explanation:
Svante Arrhenius defined acids and bases specifically for their behavior in aqueous solutions.
According to him, an acid is a substance that dissociates in water to yield hydrogen ions (\(H^+\)).
A base is a substance that dissociates in water to yield hydroxide ions (\(OH^-\)). This implies the substance itself must contain a hydroxyl group in its formula.
Evaluation of options:
- Option (A) \(H_2SO_4\): This is an Arrhenius acid because it releases \(H^+\) ions.
- Option (B) \(NH_3\): While basic, it does not have an \(OH\) group to release directly. Its basicity is explained better by the Bronsted-Lowry theory (as a proton acceptor).
- Option (C) \(NaOH\): This fits the definition perfectly. When dissolved in water, it dissociates as: \(NaOH \rightarrow Na^+ + OH^-\). It contains the hydroxyl group and releases hydroxide ions directly.
- Option (D) \(CaO\): This is a basic oxide, but it does not contain \(OH\) groups in its solid lattice. It only forms \(OH^-\) after chemically reacting with water.
Step 3: Final Answer:
Sodium hydroxide (\(NaOH\)) is the Arrhenius base because it directly releases hydroxide ions in water.