Question

What acid and what base would react in aqueous solution so that the following salts appear as products in the formula equation? Write the balanced formula equation for each reaction. a. potassium perchlorate b. cesium nitrate c. calcium iodide

Short answer

a. Potassium perchlorate (KClO4): The reaction: \(HClO4\ +\ KOH\ \longrightarrow KClO4\ +\ H2O\) b. Cesium nitrate (CsNO3): The reaction: \(HNO3\ +\ CsOH\ \longrightarrow CsNO3\ +\ H2O\) c. Calcium iodide (CaI2): The reaction: \(2HI\ +\ Ca(OH)2\ \longrightarrow CaI2\ +\ 2H2O\)

Step-by-step solution

Identify the cation and anion of the salt in each reaction

a. Potassium perchlorate (KClO4): The cation is potassium (K+) and the anion is perchlorate (ClO4-). b. Cesium nitrate (CsNO3): The cation is cesium (Cs+) and the anion is nitrate (NO3-). c. Calcium iodide (CaI2): The cation is calcium (Ca2+) and the anion is iodide (I-).

Determine which acid and base would react to produce the salts

a. Potassium perchlorate (KClO4): - Cation (K+) comes from a base containing potassium, such as potassium hydroxide (KOH). - Anion (ClO4-) comes from an acid containing perchlorate, such as perchloric acid (HClO4). The balanced formula equation is: $$ HClO4\ +\ KOH\ \longrightarrow KClO4\ +\ H2O $$ b. Cesium nitrate (CsNO3): - Cation (Cs+) comes from a base containing cesium, such as cesium hydroxide (CsOH). - Anion (NO3-) comes from an acid containing nitrate, such as nitric acid (HNO3). The balanced formula equation is: $$ HNO3\ +\ CsOH\ \longrightarrow CsNO3\ +\ H2O $$ c. Calcium iodide (CaI2): - Cation (Ca2+) comes from a base containing calcium, such as calcium hydroxide (Ca(OH)2). - Anion (I-) comes from an acid containing iodide, such as hydroiodic acid (HI). As there are two iodide ions in the salt, we will need two moles of hydroiodic acid in the balanced formula equation: $$ 2HI\ +\ Ca(OH)2\ \longrightarrow CaI2\ +\ 2H2O $$

Key concepts

Balanced Chemical Equations

Understanding balanced chemical equations is a cornerstone in learning about chemical reactions. When we talk about balancing chemical equations, we mean making sure that the number of atoms for each element involved in the reaction is the same on both the reactant side and the product side. This adherence to the law of conservation of mass ensures that no atoms are lost or created during the reaction.

For example, in the reaction to form potassium perchlorate (\texttt{KClO4}), we have perchloric acid (\texttt{HClO4}) and potassium hydroxide (\texttt{KOH}) as reactants. The balanced chemical equation becomes: \[HClO4 + KOH \longrightarrow KClO4 + H2O\] This equation shows that we have one potassium atom, one chlorine atom, and four oxygen atoms on both sides of the equation. Therefore, the equation is balanced.

Acid-Base Neutralization

Acid-base neutralization is a type of chemical reaction in which an acid and a base react to form water and a salt. The general form of this reaction can be represented as: \[\text{acid} + \text{base} \longrightarrow \text{salt} + H2O\] In these reactions, the hydrogen ions (\texttt{H+}) from the acid combine with the hydroxide ions (\texttt{OH-}) from the base to form water (\texttt{H2O}). The remaining ions from the acid and base come together to form a neutral salt. It's a perfect illustration of how substances with opposing properties can react to create more stable products. For instance, cesium nitrate (\texttt{CsNO3}) is formed through the acid-base neutralization between nitric acid (\texttt{HNO3}) and cesium hydroxide (\texttt{CsOH}):\[HNO3 + CsOH \longrightarrow CsNO3 + H2O\] By ensuring that the number of ions from both the acid and base are equivalent, we achieve a balanced and neutral outcome.

Formation of Salts

The formation of salts occurs when acids and bases neutralize each other, but understanding how these salts are derived requires examining the reactants and the resultant products closely. Each salt is composed of a positive ion, called a cation, and a negative ion, known as an anion. The cation comes from the base while the anion originates from the acid.As an illustration, let's look at calcium iodide (\texttt{CaI2}). The cation, calcium (\texttt{Ca2+}), is derived from calcium hydroxide (\texttt{Ca(OH)2}), a base. The anion, iodide (\texttt{I-}), originates from hydroiodic acid (\texttt{HI}), an acid. When these two react, they form the ionic salt calcium iodide along with water as a byproduct:\[2HI + Ca(OH)2 \longrightarrow CaI2 + 2H2O\] In this balanced chemical equation, note that two moles of hydroiodic acid are necessary because calcium iodide has two iodide ions, as evidenced by the chemical formula. This ensures that electric charge is conserved in the formation of the salt.