Answer:
NH₄⁺ will act as acid according to the arrhenius definition.
NH₄⁺ will not act as a base according to the arrhenius definition.
Explanation:
According to the Arrhenius Acid-Base Theory, acids are those substances that dissolved in water divide by generating H⁺ together with an anion (ion with a negative charge). In an aqueous solution, the H⁺ protons react immediately with the water molecules to form H₃O⁺ hydronium ions. A base, on the contrary, according to this theory, is a substance that releases OH- ions in aqueous solution.
This theory is valid only in aqueous medium. And it does not consider non-protic acids (without the presence of H⁺), which are unable to release hydrogen ions, or dehydroxylated bases (they are OH- ions in their structure), unable to release OH- hydroxyl ions.
NH₄⁺ will act as acid because it has an H⁺ proton that can be released into the aqueous solution by:
NH₄⁺(aq) + H₂O (aq) ↔ NH₃ (aq) + H₃O⁺(aq)
NH₄⁺ will not act as a base because it does not have hydroxide ions that can be released into the aqueous medium.