Step 1: Understanding the Concept:
The term "amphoteric" is derived from the Greek word \textit{amphoteros}, meaning "both." In chemistry, an amphoteric substance is one that possesses the ability to react both as an acid and as a base. This behavior can be understood through different acid-base theories. According to the Brønsted-Lowry theory, an amphoteric (or amphiprotic) substance can both donate a proton (\(H^{+}\)) and accept a proton. In terms of Lewis theory, it can both accept and donate electron pairs. Additionally, certain metal oxides are called amphoteric because they react with both strong acids and strong bases to form salts and water. Identifying an amphoteric substance requires looking for features like exchangeable protons alongside lone pairs of electrons, or an intermediate metallic character.
Step 2: Detailed Explanation:
Let's evaluate the nature of each chemical species provided in the options:
(1) NH\(_{3}\) (Ammonia): Ammonia is a well-known base because the lone pair on the nitrogen atom can accept a proton to form the ammonium ion (\(NH_{4}^{+}\)). However, under very specific conditions (such as reaction with a very strong base like metallic Sodium), Ammonia can act as an acid by losing a proton to form the amide ion (\(NH_{2}^{-}\)). Because it can technically function as both a proton donor and acceptor, it is classified as amphiprotic/amphoteric.
(2) HCl (Hydrochloric acid): HCl is one of the strongest mineral acids. In aqueous solution, it dissociates completely into \(H^{+}\) and \(Cl^{-}\). Because Chlorine is highly electronegative and the \(Cl^{-}\) ion is exceptionally stable, HCl has an overwhelming tendency to donate its proton. It has no realistic ability to accept an additional proton (\(H_{2}Cl^{+}\) is not stable in standard conditions). Therefore, HCl behaves exclusively as an acid.
(3) H\(_{2}\)O (Water): Water is the textbook example of an amphoteric substance. It can act as a base by accepting a proton to form the hydronium ion (\(H_{3}O^{+}\)) or act as an acid by donating a proton to form the hydroxide ion (\(OH^{-}\)). This dual nature is the basis for the pH scale and the auto-ionization of water.
(4) Cr\(_{2}\)O\(_{3}\) (Chromium(III) oxide): Transition metal oxides in intermediate oxidation states often show amphoteric behavior. Cr\(_{2}\)O\(_{3}\) is a green solid that does not dissolve in water but reacts with strong acids (like \(H_{2}SO_{4}\)) to form Chromium(III) salts and with strong bases (like \(NaOH\)) to form chromite complexes like \([Cr(OH)_{6}]^{3-}\).
Step 3: Comparison and Conclusion:
Among the four options, HCl stands out as a "unidirectional" chemical species. While the others can pivot their behavior depending on the reacting partner, HCl is a dedicated proton donor. It lacks the electronic or structural flexibility to act as a base.
Step 4: Final Answer:
Hydrochloric acid (HCl) is a strong acid and is not amphoteric.
Therefore, the correct answer is option (2).