Question

Ion $N{H_4}^ +$ in aqueous solution will behave as a/an:
A) Base
B) Acid
C) Both acid and base
D) Neutral

Answer 1

To solve this question, we must first understand some basic information about ammonium ions. Then we need to assess the information in a way that we can judge its acidic/basic behavior and then only we can conclude the correct answer.

Complete solution:
Before we move forward with the solution of this given question, let us first understand some basic concepts:
The ammonium cation is a positively charged polyatomic ion with the chemical formula $N{H_4}^ +$. It is formed by the protonation of ammonia $N{H_3}$ .
The degree to which ammonia forms the ammonium ion depends on the pH of the solution. If the $pH$is low, the equilibrium shifts to the right: more ammonia molecules are converted into ammonium ions. If the $pH$ is high (the concentration of hydrogen ions is low), the equilibrium shifts to the left: the hydroxide ion abstracts a proton from the ammonium ion, generating ammonia.
Ammonia, weak base in water, forms ammonium ions. It is a positively charged polyatomic ion which is mildly acidic reacting with Bronsted bases. The degree to which ammonia forms the ammonium ion depends on the $pH$ of the solution. And hence it will have the capability to donate ${H^ + }$ ions when in aqueous medium. And, Therefore $N{H_4}^ +$ ion in aqueous solution will behave as an acid.

Thus, the correct option is (B).

Note: To solve such questions we should have knowledge of what acids and bases are depending upon different kinds of theories proposed. Ammonium cation is found in a variety of salts such as ammonium carbonate, ammonium chloride and ammonium nitrate. Most simple ammonium salts are very soluble in water.