Question

For each of the following, write the molecular equation, including phase labels. Then write the net ionic equation. Note that the salts formed in these reactions are soluble. (a) the neutralization of lithium hydroxide solution by aqueous chloric acid (b) the reaction of barium hydroxide solution and aqueous nitrous acid (c) the reaction of sodium hydroxide solution and aqueous nitrous acid (d) the neutralization of aqueous hydrogen cyanide by aqueous strontium hydroxide

Short answer

The net ionic equations are the same for all reactions: \( \text{OH}^- + \text{H}^+ \rightarrow \text{H}_2\text{O} \)

Step-by-step solution

Write the Molecular Equation for (a)

The neutralization reaction between lithium hydroxide \( \text{LiOH} \) and chloric acid \( \text{HClO}_3 \) can be represented as follows:\[ \text{LiOH (aq) + HClO}_3 \text{(aq) } \rightarrow \text{ LiClO}_3 \text{(aq) } + \text{ H}_2\text{O (l)} \]

Write the Net Ionic Equation for (a)

Since \( \text{LiClO}_3 \) is soluble and dissociates fully, we can cancel the spectator ions. The net ionic equation is:\[ \text{OH}^- \text{(aq) + } \text{H}^+ \text{(aq) } \rightarrow \text{ H}_2\text{O (l)} \]

Write the Molecular Equation for (b)

The reaction between barium hydroxide \( \text{Ba(OH)}_2 \) and nitrous acid \( \text{HNO}_2 \) is:\[ \text{Ba(OH)}_2 \text{(aq) + 2 HNO}_2 \text{(aq) } \rightarrow \text{Ba(NO}_2\text{)}_2 \text{(aq) + 2 H}_2\text{O(l)} \]

Write the Net Ionic Equation for (b)

Both \( \text{Ba(NO}_2\text{)}_2 \) and water are the products, with water being the compound of interest. The net ionic equation simplifies to:\[ \text{2 OH}^- \text{(aq) + 2 H}^+ \text{(aq) } \rightarrow \text{ 2 H}_2\text{O(l)} \]

Write the Molecular Equation for (c)

For sodium hydroxide \( \text{NaOH} \) with nitrous acid \( \text{HNO}_2 \), the molecular equation is:\[ \text{NaOH(aq) + HNO}_2 \text{(aq) } \rightarrow \text{NaNO}_2 \text{(aq) + H}_2\text{O(l)} \]

Write the Net Ionic Equation for (c)

The sodium ions and nitrite ions do not participate in the reaction, so the net ionic equation for neutralizing OH⁻ by H⁺ is:\[ \text{OH}^- \text{(aq) + H}^+ \text{(aq) } \rightarrow \text{ H}_2\text{O(l)} \]

Write the Molecular Equation for (d)

The reaction with hydrogen cyanide \( \text{HCN} \) and strontium hydroxide \( \text{Sr(OH)}_2 \) gives:\[ \text{2 HCN(aq) + Sr(OH)}_2 \text{(aq) } \rightarrow \text{Sr(CN)}_2 \text{(aq) + 2 H}_2\text{O(l)} \]

Write the Net Ionic Equation for (d)

The major ionic reaction is the neutralization. Only the ions to form water stay in reaction in ionic form:\[ \text{2 H}^+ \text{(aq) + 2 OH}^- \text{(aq) } \rightarrow \text{ 2 H}_2\text{O(l)} \]

Key concepts

Neutralization Reactions

Neutralization reactions are essential in chemistry as they involve the reaction of an acid and a base to form water and a salt. These processes help control the pH levels in various systems, both industrially and biologically. In the context of neutralization, the key players are hydrogen ions (H\(^+\)) from acids and hydroxide ions (OH\(^-\)) from bases. When these ions come together, they form water, H\(_2\)O, a very stable compound. Neutralization reactions are exothermic, meaning they release heat as the reaction proceeds. This heat release is often harnessed in applications ranging from everyday heat packs to intricate chemical manufacturing processes.

Molecular Equations

Molecular equations play a vital role in providing an overall picture of chemical reactions. They display all reactants and products in their complete formula form. Each participant in the reaction is shown with its specific chemical formula along with its state of matter, which is usually indicated by (s) for solids, (l) for liquids, (g) for gases, and (aq) for aqueous solutions. For example, in the reaction of lithium hydroxide with chloric acid, the molecular equation is written as: \[ \text{LiOH (aq) + HClO}_3 \text{(aq) } \rightarrow \text{LiClO}_3 \text{(aq) } + \text{H}_2\text{O (l)} \]This notation enables chemists to efficiently communicate the substances involved and the transformations that occur in a reaction. While molecular equations provide a full view, they need further processing to reveal the ions actually participating in the chemical change.

Solubility of Salts

Solubility is a fundamental property defining the amount of a solute that can dissolve in a solvent at a given temperature. In the context of salts, solubility helps predict whether or not a compound will dissolve in water, forming an aqueous solution. Soluble salts dissociate into ions when dissolved, which is crucial for their role in ionic equations. For instance, when lithium chlorate is dissolved in water, it splits into lithium and chlorate ions due to its high solubility. Being able to predict the solubility of compounds is essential for writing accurate net ionic equations, understanding reactions, and applying them to practical scenarios, like predicting precipitation reactions or crafting medicines.

Ionic Reactions in Chemistry

Ionic reactions involve the exchange of ions in a solution and are a cornerstone of aqueous chemistry. Unlike molecular equations, ionic equations break down compounds into their constituent ions to emphasize the actual chemical processes taking place. For instance, in net ionic equations, we only show the ions that actively participate in a reaction, eliminating those that do not change throughout the process, known as spectator ions. Taking the reaction between hydroxide and hydrogen ions:\[ \text{OH}^- \text{(aq) + H}^+ \text{(aq) } \rightarrow \text{H}_2\text{O(l)} \]This highlights the essence of how ions interact and bond to form new substances, like water in neutralization reactions. Understanding ionic reactions is pivotal in fields such as analytical chemistry, where it lends insight into reaction mechanisms and stoichiometry.