Question

Complete and balance the following Bronsted-Lowry neutralization reactions: (a) \(\mathrm{HF}(a q)+\mathrm{NaHS}(a q) \longrightarrow\) (b) \(\mathrm{HNO}_{2}(a q)+\mathrm{NaC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}(a q) \longrightarrow\)

Short answer

(a) \(\text{NaF}(aq) + \text{H}_2\text{S}(g)\); (b) \(\text{NaNO}_2(aq) + \text{HC}_2\text{H}_3\text{O}_2(aq)\).

Step-by-step solution

Identify the Bronsted-Lowry Acid and Base

In reaction (a), \( \text{HF} \) is the acid because it donates a proton (H\(^+\)), and \( \text{NaHS} \) acts as a base because it can accept a proton. In reaction (b), \( \text{HNO}_2 \) serves as the Bronsted-Lowry acid and \( \text{NaC}_2 \text{H}_3\text{O}_2 \) is the base.

Predict the Products

For reaction (a), the acid \( \text{HF} \) donates a proton to the base \( \text{NaHS} \), forming \( \text{NaF} \) and \( \text{H}_2\text{S} \). Therefore, the products are \( \text{NaF} (aq) + \text{H}_2\text{S} (g) \). For reaction (b), the \( \text{HNO}_2 \) donates a proton to acetate ion \( \text{C}_2 \text{H}_3\text{O}_2^-\) to form \( \text{HC}_2 \text{H}_3\text{O}_2 \) and \( \text{NO}_2^- \). This yields the products \( \text{NaNO}_2 \) and \( \text{HC}_2\text{H}_3\text{O}_2 \).

Balance the Chemical Equations

Reaction (a) is already balanced as \( \text{HF} (aq) + \text{NaHS} (aq) \rightarrow \text{NaF} (aq) + \text{H}_2\text{S} (g) \). For reaction (b), ensure both products and reactants are equal on both sides, resulting in balanced reaction: \( \text{HNO}_2 (aq) + \text{NaC}_2\text{H}_3\text{O}_2 (aq) \rightarrow \text{NaNO}_2 (aq) + \text{HC}_2\text{H}_3\text{O}_2 (aq) \).

Key concepts

Acid-Base Reactions

Acid-base reactions are fascinating chemical processes crucial to understanding many aspects of chemistry. These reactions involve the transfer of protons from an acid to a base. The Bronsted-Lowry theory is a popular model used to describe these reactions. It defines an acid as a proton donor and a base as a proton acceptor. In this context, a proton generally refers to a hydrogen cation, H extsuperscript{+}.

One key feature of acid-base reactions is that they often result in the formation of water and a salt. For example, when hydrochloric acid reacts with sodium hydroxide, water and sodium chloride are produced.

Understanding acid-base reactions involves recognizing the compounds that can either donate or accept protons. Once this recognition occurs, predicting the outcome of the reactions becomes straightforward as you can foresee the resulting formation of new compounds, typically through the neutralization process.

Chemical Equations

Chemical equations act as a symbolic representation of chemical reactions. They comprise reactants (starting substances) and products (substances formed from the reactants). These equations must be balanced to comply with the law of conservation of mass, meaning that the number of atoms of each element should be equal on both sides of the equation.

Balancing chemical equations involves adjusting coefficients before the compounds to ensure the elements are balanced correctly. Take the neutralization reaction involving \( \text{HF} (aq) + \text{NaHS} (aq) \rightarrow \text{NaF} (aq) + \text{H}_2\text{S} (g) \). This reaction is already balanced. Each element appears the same number of times on both sides of the equation.

In some cases, balancing may require recognizing compounds that can dissociate in solution or understanding how different ionic charges balance out. For instance, reactions involving polyatomic ions require careful consideration to ensure these entities are evenly balanced as single units.

Proton Transfer Reactions

Proton transfer reactions are the foundation of Bronsted-Lowry acid-base chemistry. These reactions are characterized by the transfer of hydrogen cations, referred to as protons, from an acid to a base. In any given reaction, this transfer simplifies down into the exchange of these protons between the respective reactants.

In this type of reaction, the acid's capability to donate a proton is critical. For example, in the neutralization of \( \text{HF} (aq) + \text{NaHS} (aq) \rightarrow \text{NaF} (aq) + \text{H}_2\text{S} (g) \), the HF molecule donates a proton to the NaHS, showing classic proton transfer characteristics.

Upon proton donation, the acid is transformed into its conjugate base, while the base, upon accepting the proton, forms its respective conjugate acid. These conjugate pairs are a telling feature of proton transfer reactions and help in determining the direction of the reaction's equilibrium and its overall spontaneity.