Question

What strong acid and what strong base would react in aqueous solution to produce the following salts? a. potassium perchlorate, \(\mathrm{KClO}_{4}\) b. cesium nitrate, \(\mathrm{CsNO}_{3}\) c. potassium chloride, \(\mathrm{KCl}\) d. sodium sulfate, \(\mathrm{Na}_{2} \mathrm{SO}_{4}\)

Short answer

a. Potassium perchlorate, \(\mathrm{KClO}_{4}\): Perchloric acid (\(\mathrm{HClO}_{4}\)) and Potassium hydroxide (\(\mathrm{KOH}\)) b. Cesium nitrate, \(\mathrm{CsNO}_{3}\): Nitric acid (\(\mathrm{HNO}_{3}\)) and Cesium hydroxide (\(\mathrm{CsOH}\)) c. Potassium chloride, \(\mathrm{KCl}\): Hydrochloric acid (\(\mathrm{HCl}\)) and Potassium hydroxide (\(\mathrm{KOH}\)) d. Sodium sulfate, \(\mathrm{Na}_{2} \mathrm{SO}_{4}\): Sulfuric acid (\(\mathrm{H}_{2}\mathrm{SO}_{4}\)) and Sodium hydroxide (\(\mathrm{NaOH}\))

Step-by-step solution

Identify the cation and anion in each salt.

For each salt, we need to identify the positive cation and the negative anion. We will do this by looking at the formula of the salt and the periodic table to determine the charge of each ion. a. Potassium perchlorate, \(\mathrm{KClO}_{4}\) Cation: Potassium (K\(^{+}\)) Anion: Perchlorate (ClO\(_{4}^-\)) b. Cesium nitrate, \(\mathrm{CsNO}_{3}\) Cation: Cesium (Cs\(^{+}\)) Anion: Nitrate (NO\(_{3}^-\)) c. Potassium chloride, \(\mathrm{KCl}\) Cation: Potassium (K\(^{+}\)) Anion: Chloride (Cl\(^-\)) d. Sodium sulfate, \(\mathrm{Na}_{2} \mathrm{SO}_{4}\) Cation: Sodium (Na\(^{+}\)) Anion: Sulfate (SO\(_{4}^{2-}\))

Find the corresponding strong acid and strong base for each salt.

Now that we know the cation and anion for each salt, we can find the strong acid and strong base that will react to produce the salt. Remember that strong acids and strong bases dissociate completely in water, so we are looking for the acid and base that contain the same ions as the salt. a. Potassium perchlorate, \(\mathrm{KClO}_{4}\) Strong Acid: Perchloric acid, \(\mathrm{HClO}_{4}\) (contains the ClO\(_{4}^-\) anion) Strong Base: Potassium hydroxide, \(\mathrm{KOH}\) (contains the K\(^{+}\) cation) Reaction: \(\mathrm{HClO}_{4}\) + \(\mathrm{KOH}\) -> \(\mathrm{KClO}_{4}\) + \(\mathrm{H}_{2}\mathrm{O}\) b. Cesium nitrate, \(\mathrm{CsNO}_{3}\) Strong Acid: Nitric acid, \(\mathrm{HNO}_{3}\) (contains the NO\(_{3}^-\) anion) Strong Base: Cesium hydroxide, \(\mathrm{CsOH}\) (contains the Cs\(^{+}\) cation) Reaction: \(\mathrm{HNO}_{3}\) + \(\mathrm{CsOH}\) -> \(\mathrm{CsNO}_{3}\) + \(\mathrm{H}_{2}\mathrm{O}\) c. Potassium chloride, \(\mathrm{KCl}\) Strong Acid: Hydrochloric acid, \(\mathrm{HCl}\) (contains the Cl\(^-\) anion) Strong Base: Potassium hydroxide, \(\mathrm{KOH}\) (contains the K\(^{+}\) cation) Reaction: \(\mathrm{HCl}\) + \(\mathrm{KOH}\) -> \(\mathrm{KCl}\) + \(\mathrm{H}_{2}\mathrm{O}\) d. Sodium sulfate, \(\mathrm{Na}_{2}\mathrm{SO}_{4}\) Strong Acid: Sulfuric acid, \(\mathrm{H}_{2}\mathrm{SO}_{4}\) (contains the SO\(_{4}^{2-}\) anion) Strong Base: Sodium hydroxide, \(\mathrm{NaOH}\) (contains the Na\(^{+}\) cation) Reaction: \(\mathrm{H}_{2}\mathrm{SO}_{4}\) + 2\(\mathrm{NaOH}\) -> \(\mathrm{Na}_{2}\mathrm{SO}_{4}\) + 2\(\mathrm{H}_{2}\mathrm{O}\)

Key concepts

Salt Formation

Salts are fascinating compounds formed from the neutralization reaction between an acid and a base. When a strong acid reacts with a strong base, they dissociate completely in an aqueous solution. As a result, their respective ions come together to form a salt. These salts are typically soluble and do not retain the acidic or basic characteristics of their parent compounds.

During neutralization, the hydrogen ions from the acid react with the hydroxide ions from the base, typically producing water. The remaining ions form the salt. In our examples, we can see:

• Potassium perchlorate (\(\mathrm{KClO}_{4}\)) forms with perchloric acid and potassium hydroxide.
• Cesium nitrate (\(\mathrm{CsNO}_{3}\)) is the product of nitric acid combining with cesium hydroxide.
• Potassium chloride (\(\mathrm{KCl}\)) results from hydrochloric acid and potassium hydroxide.
• Sodium sulfate (\(\mathrm{Na}_{2} \mathrm{SO}_{4}\)) forms when sulfuric acid reacts with sodium hydroxide.

All these salts show the general concept of a strong acid-base reaction leading to water and salt formation.

Cation and Anion Identification

In chemistry, identifying the ions that make up a salt is essential for understanding its properties and reactions. Every salt consists of a positive ion, called a cation, and a negative ion, called an anion. The formula for a salt provides clues to the identities of these ions.

For example, in potassium perchlorate (\(\mathrm{KClO}_{4}\)), the cation is potassium (\(\mathrm{K}^+\)), and the anion is perchlorate (\(\mathrm{ClO}_{4}^{-}\)). Similarly, in cesium nitrate (\(\mathrm{CsNO}_{3}\)), we find cesium (\(\mathrm{Cs}^+\)) as the cation and nitrate (\(\mathrm{NO}_{3}^-\)) as the anion.

For potassium chloride (\(\mathrm{KCl}\)), the ions are potassium (\(\mathrm{K}^+\)) and chloride (\(\mathrm{Cl}^-\)). Lastly, sodium sulfate (\(\mathrm{Na}_{2} \mathrm{SO}_{4}\)) contains sodium (\(\mathrm{Na}^+\)) cations and sulfate (\(\mathrm{SO}_{4}^{2-}\)) anions.

• Identifying these ions is critical for predicting how salts will react and interact in different chemical solutions.
• Knowing the cations and anions is also necessary for balancing chemical equations accurately.

Reaction Equations

Reaction equations provide a compact way to describe what happens during a chemical reaction. In strong acid-base reactions, these equations become particularly important as they illustrate how reactants transform into products.

The general form of such a reaction is a strong acid combining with a strong base to produce a salt and water. Let's review the reactions for the salts we discussed:

• For potassium perchlorate, the equation is \(\mathrm{HClO}_{4} + \mathrm{KOH} \rightarrow \mathrm{KClO}_{4} + \mathrm{H}_{2}\mathrm{O}\).
• Cesium nitrate results from \(\mathrm{HNO}_{3} + \mathrm{CsOH} \rightarrow \mathrm{CsNO}_{3} + \mathrm{H}_{2}\mathrm{O}\).
• Potassium chloride forms with \(\mathrm{HCl} + \mathrm{KOH} \rightarrow \mathrm{KCl} + \mathrm{H}_{2}\mathrm{O}\).
• Sodium sulfate is produced by \(\mathrm{H}_{2}\mathrm{SO}_{4} + 2\mathrm{NaOH} \rightarrow \mathrm{Na}_{2}\mathrm{SO}_{4} + 2\mathrm{H}_{2}\mathrm{O}\).

Each equation shows the complete neutralization and the resulting products, emphasizing the conservation of mass and charge in chemical reactions. Understanding these equations helps students predict reaction outcomes and verify their accuracy in lab settings or theoretical exercises.