Out of the following compounds, which can only be an Arrhenius acid?

• A. NaCl
• B. Sr(OH)₂
• C. H₂O
• D. CH₃COOH
• E. NH₃

Answer: (D)

Verified step by step guidance

1. Recall the definition of an Arrhenius acid: a substance that increases the concentration of H\(\textsuperscript{+}\) ions (protons) in aqueous solution.
2. Analyze each compound to determine if it increases H\(\textsuperscript{+}\) ions when dissolved in water:
3. a) NaCl is a salt that dissociates into Na\(\textsuperscript{+}\) and Cl\(\textsuperscript{-}\), neither of which increases H\(\textsuperscript{+}\) concentration, so it is not an Arrhenius acid.
4. b) Sr(OH)\(\textsubscript{2}\) is a strong base that dissociates to produce OH\(\textsuperscript{-}\) ions, increasing hydroxide concentration, so it is an Arrhenius base, not an acid.
5. c) H\(\textsubscript{2}\)O is neutral and can act as both acid and base (amphoteric), but it does not solely increase H\(\textsuperscript{+}\) concentration, so it is not only an Arrhenius acid.
6. d) CH\(\textsubscript{3}\)COOH (acetic acid) dissociates to produce H\(\textsuperscript{+}\) ions in solution, fitting the Arrhenius acid definition exclusively.
7. e) NH\(\textsubscript{3}\) is a base that increases OH\(\textsuperscript{-}\) concentration by accepting H\(\textsuperscript{+}\), so it is not an Arrhenius acid.