Question

According to the Bronsted-Lowry theory, label each of the following as an acid or a base. (a) \(\mathrm{HNO}_{2}\) (b) \(\mathrm{OCl}^{-} ;(\mathrm{c}) \mathrm{NH}_{2}^{-} ;\) (d) \(\mathrm{NH}_{4}^{+} ;\) (e) \(\mathrm{CH}_{3} \mathrm{NH}_{3}^{+}\)

Short answer

(a) \(\mathrm{HNO}_{2}\) is an acid. (b) \(\mathrm{OCl}^{-}\) is a base. (c) \(\mathrm{NH}_{2}^{-}\) is a base. (d) \(\mathrm{NH}_{4}^{+}\) is an acid. (e) \(\mathrm{CH}_{3} \mathrm{NH}_{3}^{+}\) is an acid.

Step-by-step solution

Identify Proton Donors and Acceptors

According to the Bronsted-Lowry theory, we're going to identify if each substance in the exercise can donate a proton (making it an acid) or if it can accept a proton (making it a base).

Classify \(\mathrm{HNO}_{2}\)

\(\mathrm{HNO}_{2}\) has a hydrogen atom that it can donate. Thus, \(\mathrm{HNO}_{2}\) is a Bronsted-Lowry acid.

Classify \(\mathrm{OCl}^{-}\)

\(\mathrm{OCl}^{-}\) is a negative ion and can accept an extra hydrogen ion. Thus, \(\mathrm{OCl}^{-}\) is a Bronsted-Lowry base.

Classify \(\mathrm{NH}_{2}^{-}\)

\(\mathrm{NH}_{2}^{-}\) is a negative ion and can accept a extra hydrogen ion. Thus, \(\mathrm{NH}_{2}^{-}\) is a Bronsted-Lowry base.

Classify \(\mathrm{NH}_{4}^{+}\)

\(\mathrm{NH}_{4}^{+}\) can donate one of its hydrogen ions. Thus, \(\mathrm{NH}_{4}^{+}\) is a Bronsted-Lowry acid.

Classify \(\mathrm{CH}_{3} \mathrm{NH}_{3}^{+}\)

\(\mathrm{CH}_{3}\mathrm{NH}_{3}^{+}\) can donate one of its hydrogen ions indicated by its positive charge. Thus, \(\mathrm{CH}_{3}\mathrm{NH}_{3}^{+}\) is a Bronsted-Lowry acid.

Key concepts

Acid-Base Reactions

The concept of acid-base reactions is central to the Bronsted-Lowry theory. This theory expands our understanding of how substances interact in chemical reactions. An acid-base reaction involves two key players: acids and bases. Here, the main action is the transfer of a proton (H⁺ ion) from one substance to another. The substance that donates the proton, known as the acid, decreases in hydrogen content.

Meanwhile, the base receives the proton, becoming richer in hydrogen. This exchange is crucial for various biological and chemical processes, from digestion to the formation of salts. Each participant in the reaction plays a specific role, either as a proton donor or acceptor.

A classic example can be seen when hydrochloric acid ( HCl ) interacts with water to form hydronium ions ( H_3O^+ ), with water acting as the base accepting the proton.

Proton Donors

In the Bronsted-Lowry theory, proton donors are called acids. An acid is any substance that can give away a proton to another substance. This donation process is crucial for the formation of certain compounds and plays a vital role in the chemical industry and nature.

Let's discuss an example: HNO_2 , or nitrous acid. In an acid-base reaction, it has the potential to give up one of its hydrogen ions, showcasing its ability to act as a Bronsted-Lowry acid. Other substances, such as NH_4^+ (ammonium) and CH_3NH_3^+ (methylammonium), also exhibit this behavior since they have a positive charge due to an extra proton and are willing to donate it to a base.

• Acids play vital roles in various reactions.
• Their ability to donate protons helps drive many biological and industrial processes.

Recognizing compounds that can act as proton donors helps us understand and predict their behavior in chemical reactions.

Proton Acceptors

On the other side of the coin, we have proton acceptors, known as bases in the Bronsted-Lowry model. A base is any substance that has the ability to accept a proton, and this interaction is key to completing many reactions.

The curiosity arises when considering substances like OCl^- (hypochlorite) and NH_2^- (amide). These are examples of Bronsted-Lowry bases. Their negative charge indicates they can readily accept a proton. This makes them prone to interacting with acids, thereby neutralizing their effect in some cases.

• Bases balance the reaction by accepting protons.
• They are fundamental in neutralizing acids, crucial for reactions such as saponification in soap making.

Understanding which substances serve as proton acceptors enhances our knowledge of their behavior and role in chemical reactions.