Question

Identify each of the following unbalanced reaction equations as belonging to one or more of the following categories: precipitation, acid-base, or oxidation-reduction. a. \(\mathrm{H}_{2} \mathrm{O}_{2}(a q) \rightarrow \mathrm{H}_{2} \mathrm{O}(l)+\mathrm{O}_{2}(g)\) b. \(\mathrm{H}_{2} \mathrm{SO}_{4}(a q)+\mathrm{Cu}(s) \rightarrow \mathrm{CuSO}_{4}(a q)+\mathrm{H}_{2}(g)\) c. \(\mathrm{H}_{2} \mathrm{SO}_{4}(a q)+\mathrm{NaOH}(a q) \rightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}(a q)+\mathrm{H}_{2} \mathrm{O}(l)\) d. \(\mathrm{H}_{2} \mathrm{SO}_{4}(a q)+\mathrm{Ba}(\mathrm{OH})_{2}(a q) \rightarrow \mathrm{BaSO}_{4}(s)+\mathrm{H}_{2} \mathrm{O}(l)\) e. \(\mathrm{AgNO}_{3}(a q)+\mathrm{CuCl}_{2}(a q) \rightarrow \mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}(a q)+\) \(\mathrm{AgCl}(s)\) f. \(\mathrm{KOH}(a q)+\mathrm{CuSO}_{4}(a q) \rightarrow \mathrm{Cu}(\mathrm{OH})_{2}(s)+\mathrm{K}_{2} \mathrm{SO}_{4}(a q)\) g. \(\mathrm{Cl}_{2}(g)+\mathrm{F}_{2}(g) \rightarrow \operatorname{ClF}(g)\) h. \(\mathrm{NO}(g)+\mathrm{O}_{2}(g) \rightarrow \mathrm{NO}_{2}(g)\) i. \(\mathrm{Ca}(\mathrm{OH})_{2}(s)+\mathrm{HNO}_{3}(a q) \rightarrow \mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l)\)

Short answer

a. Oxidation-reduction b. Oxidation-reduction c. Acid-base d. Precipitation, Acid-base e. Precipitation, Oxidation-reduction f. Precipitation g. Oxidation-reduction h. Oxidation-reduction i. Acid-base

Step-by-step solution

Identify the type of reaction for equation a

For the reaction: \(\mathrm{H}_{2} \mathrm{O}_{2}(a q) \rightarrow \mathrm{H}_{2} \mathrm{O}(l)+\mathrm{O}_{2}(g)\) There is no solid formed, and no proton transfer occurs. However, we do have a change in oxidation states for oxygen, as it goes from -1 in \(\mathrm{H}_{2} \mathrm{O}_{2}\) to -2 in \(\mathrm{H}_{2} \mathrm{O}\) and 0 in \(\mathrm{O}_{2}\). Therefore, this reaction is an oxidation-reduction reaction.

Identify the type of reaction for equation b

For the reaction: \(\mathrm{H}_{2} \mathrm{SO}_{4}(a q)+\mathrm{Cu}(s) \rightarrow \mathrm{CuSO}_{4}(a q)+\mathrm{H}_{2}(g)\) There is no solid formed, and no proton transfer occurs. However, we do have a change in oxidation states for both hydrogen and copper. Therefore, this reaction is an oxidation-reduction reaction.

Identify the type of reaction for equation c

For the reaction: \(\mathrm{H}_{2} \mathrm{SO}_{4}(a q)+\mathrm{NaOH}(a q) \rightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}(a q)+\mathrm{H}_{2} \mathrm{O}(l)\) Here, we have a transfer of protons from \(\mathrm{H}_{2} \mathrm{SO}_{4}\) to \(\mathrm{NaOH}\), making this an acid-base reaction. There is no solid formed and no significant changes in oxidation states.

Identify the type of reaction for equation d

For the reaction: \(\mathrm{H}_{2} \mathrm{SO}_{4}(a q)+\mathrm{Ba}(\mathrm{OH})_{2}(a q) \rightarrow \mathrm{BaSO}_{4}(s)+\mathrm{H}_{2} \mathrm{O}(l)\) We have a solid formed, which is \(\mathrm{BaSO}_{4}\), making this a precipitation reaction. Additionally, we can see that protons are transferred from \(\mathrm{H}_{2} \mathrm{SO}_{4}\) to \(\mathrm{Ba}(\mathrm{OH})_{2}\), making this also an acid-base reaction. There are no significant changes in oxidation states.

Identify the type of reaction for equation e

For the reaction: \(\mathrm{AgNO}_{3}(a q)+\mathrm{CuCl}_{2}(a q) \rightarrow \mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}(a q)+\mathrm{AgCl}(s)\) A solid is formed, \(\mathrm{AgCl}\), making this a precipitation reaction. Additionally, we have a change in oxidation states for silver and copper, making this an oxidation-reduction reaction as well. There is no proton transfer.

Identify the type of reaction for equation f

For the reaction: \(\mathrm{KOH}(a q)+\mathrm{CuSO}_{4}(a q) \rightarrow \mathrm{Cu}(\mathrm{OH})_{2}(s)+\mathrm{K}_{2} \mathrm{SO}_{4}(a q)\) As we have a solid being formed, \(\mathrm{Cu}(\mathrm{OH})_{2}\), this is a precipitation reaction. There is no proton transfer and no significant changes in oxidation states.

Identify the type of reaction for equation g

For the reaction: \(\mathrm{Cl}_{2}(g)+\mathrm{F}_{2}(g) \rightarrow \operatorname{ClF}(g)\) There is no solid formed and no proton transfer. However, we have a change in the oxidation state for both chlorine and fluorine. Therefore, this reaction is an oxidation-reduction reaction.

Identify the type of reaction for equation h

For the reaction: \(\mathrm{NO}(g)+\mathrm{O}_{2}(g) \rightarrow \mathrm{NO}_{2}(g)\) There is no solid formed and no proton transfer. However, we have a change in the oxidation state for nitrogen and oxygen. Therefore, this reaction is an oxidation-reduction reaction.

Identify the type of reaction for equation i

For the reaction: \(\mathrm{Ca}(\mathrm{OH})_{2}(s)+\mathrm{HNO}_{3}(a q) \rightarrow \mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l)\) In this reaction, protons are transferred from \(\mathrm{HNO}_{3}\) to \(\mathrm{Ca}(\mathrm{OH})_{2}\), making this an acid-base reaction. There is no solid formed and no significant changes in oxidation states.

Key concepts

Precipitation Reaction

A precipitation reaction is a type of chemical reaction where a solid, called a precipitate, forms when two aqueous solutions are combined. This solid results from the reaction between ions that produce an insoluble compound. Precipitation reactions are often used to isolate a particular compound from a solution, and they play a fundamental role in various fields such as chemistry, environmental science, and medicine.

For example, if you mix aqueous solutions of silver nitrate (\textbf{AgNO}\(_{3}\)) and copper(II) chloride (\textbf{CuCl}\(_2\)), a white solid of silver chloride (\textbf{AgCl}) forms. The reaction can be represented as follows:
\textbf{AgNO}\(_{3}\)(aq) + \textbf{CuCl}\(_{2}\)(aq) \rightarrow \textbf{Cu}(\textbf{NO}\(_{3}\))\(_{2}\)(aq) + \textbf{AgCl}(s)

This is a classic example of a precipitation reaction because the solid silver chloride is the precipitate, and it is visibly distinguishable from the rest of the reactants and products which remain in the solution.

Acid-Base Reaction

An acid-base reaction involves the transfer of protons (H\(^+\) ions) from one reactant to another. These reactions are also known as neutralization reactions, where an acid and a base react to form water and a salt. Acids are proton donors, while bases are proton acceptors. When these substances are mixed in aqueous solutions, the H\(^+\) ions from the acid combine with the OH\(^-\) ions from the base to produce water (H\(_2\)O).

For instance, when sulfuric acid (\textbf{H}\(_2\)\textbf{SO}\(_4\)) reacts with sodium hydroxide (\textbf{NaOH}), the resulting reaction yields sodium sulfate (\textbf{Na}\(_2\)\textbf{SO}\(_4\)) and water, as shown below:
\textbf{H}\(_2\)\textbf{SO}\(_4\)(aq) + 2\textbf{NaOH}(aq) \rightarrow \textbf{Na}\(_2\)\textbf{SO}\(_4\)(aq) + 2\textbf{H}\(_2\)\textbf{O}(l)

Acid-base reactions are crucial in many biological and environmental processes, including the buffering of blood in the human body and the treatment of wastewater.

Oxidation-Reduction Reaction

Oxidation-reduction reactions, commonly known as redox reactions, involve the transfer of electrons between substances, leading to a change in their oxidation states. These reactions are fundamental to energy transfer processes in biological systems and industrial applications such as battery technology. In a redox reaction, the substance that loses electrons is oxidized, and the substance that gains electrons is reduced.

As an illustrative example, when hydrogen peroxide (\textbf{H}\(_2\)\textbf{O}\(_2\)) decomposes into water and oxygen, it's an oxidation-reduction reaction. Here, oxygen in hydrogen peroxide goes from an oxidation state of -1 to -2 in water and 0 in molecular oxygen (O\(_2\)), as seen in the reaction:
\textbf{H}\(_2\)\textbf{O}\(_2\)(aq) \rightarrow 2\textbf{H}\(_2\)\textbf{O}(l) + \textbf{O}\(_2\)(g)

In this reaction, hydrogen peroxide acts as both an oxidizing and a reducing agent since it is reduced to water and oxidized to oxygen. Understanding redox reactions is crucial for a plethora of chemical processes including metabolism, rusting, and combustion.