Question

Identify the Arrhenius acid and Arrhenius base in each of the following neutralization reactions: (a) \(\mathrm{HI}(a q)+\mathrm{NaOH}(a q) \longrightarrow \operatorname{NaI}(a q)+\mathrm{H}_{2} \mathrm{O}(l)\) (b) \(\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}(a q)+\mathrm{LiOH}(a q) \longrightarrow \mathrm{LiC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l)\)

Short answer

(a) HI is the acid, NaOH is the base. (b) HC₂H₃O₂ is the acid, LiOH is the base.

Step-by-step solution

Identify the Components

In each reaction, identify the compounds that can donate a proton (H⁺) and that can donate a hydroxide ion (OH⁻). These will be your potential Arrhenius acids and bases.

Definition of Arrhenius Acid and Base

According to Arrhenius theory, an acid is a substance that increases the concentration of hydrogen ions (H⁺) in an aqueous solution, and a base is a substance that increases the concentration of hydroxide ions (OH⁻) in an aqueous solution.

Identify Arrhenius Acid and Base in Reaction (a)

In the reaction \( \text{HI} + \text{NaOH} \rightarrow \text{NaI} + \text{H}_2\text{O} \): \( \text{HI} \) is the acid because it donates a hydrogen ion to form \( \text{I}^- \), and \( \text{NaOH} \) is the base because it donates a hydroxide ion (OH⁻).

Identify Arrhenius Acid and Base in Reaction (b)

In the reaction \( \text{HC}_2\text{H}_3\text{O}_2 + \text{LiOH} \rightarrow \text{LiC}_2\text{H}_3\text{O}_2 + \text{H}_2\text{O} \): \( \text{HC}_2\text{H}_3\text{O}_2 \) acts as the acid by donating a proton (H⁺), and \( \text{LiOH} \) is the base as it donates a hydroxide ion (OH⁻).

Key concepts

Neutralization Reactions

Neutralization reactions are a fascinating aspect of chemistry where an acid reacts with a base to produce a salt and water. During this process, the acidic hydrogen ion \((H^+)\) from the acid combines with the basic hydroxide ion \((OH^-)\) from the base to form water \((H_2O)\). This reaction is not only common in labs but also has practical applications in everyday life, such as in antacids and agricultural lime.

In a typical neutralization reaction, the following occurs:

• An acid provides \((H^+)\) ions.
• A base supplies \((OH^-)\) ions.
• The \((H^+)\) and \((OH^-)\) ions then combine to form water.
• The leftover ions from the acid and base form a salt.

For instance, when hydrochloric acid \((HCl)\) reacts with sodium hydroxide \((NaOH)\), the process forms water \((H_2O)\) and sodium chloride \((NaCl)\), which is common table salt. Understanding how these reactions occur can help in predicting the results of mixing various acids and bases.

Arrhenius Acid

An Arrhenius acid is defined as a substance that increases the concentration of hydrogen ions \((H^+)\) when dissolved in water. This definition, introduced by the Swedish chemist Svante Arrhenius, focuses on the behavior of substances in aqueous solutions. When an Arrhenius acid dissolves, it dissociates to release \(H^+\) ions into the solution.

Some common examples of Arrhenius acids include:

• Hydrochloric acid \((HCl)\)
• Sulfuric acid \((H_2SO_4)\)
• Nitric acid \((HNO_3)\)
• Acetic acid \((HC_2H_3O_2)\)

In the reactions given in the exercise, \(HI\) in part (a) and \(HC_2H_3O_2\) in part (b) serve as Arrhenius acids. Each of these compounds dissociates in water to increase the presence of \(H^+\) ions, characterizing them as acids according to Arrhenius' concept.

Arrhenius Base

An Arrhenius base is a substance that increases the concentration of hydroxide ions \((OH^-)\) in an aqueous solution. According to Arrhenius' theory, when such a base dissolves, it separates into ions and releases hydroxide ions which interact readily with hydrogen ions in a neutralization reaction.

A few well-known Arrhenius bases are:

• Sodium hydroxide \((NaOH)\)
• Potassium hydroxide \((KOH)\)
• Calcium hydroxide \((Ca(OH)_2)\)
• Lithium hydroxide \((LiOH)\)

In the given exercises, \(NaOH\) and \(LiOH\) are identified as the Arrhenius bases due to their release of \(OH^-\) ions in their respective reactions. By understanding how Arrhenius bases operate, you can easily predict their behavior in chemical reactions, especially neutralizations.