Problem 27 - General Chemistry: Principles and Modern Applications

Question

Complete each of the following as a net ionic equation. If no reaction occurs, so state. (a) \(\mathrm{Ba}^{2+}+2 \mathrm{OH}^{-}+\mathrm{CH}_{3} \mathrm{COOH} \longrightarrow\) (b) \(\mathrm{H}^{+}+\mathrm{Cl}^{-}+\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COOH} \longrightarrow\) (c) \(\operatorname{FeS}(\mathrm{s})+\mathrm{H}^{+}+\mathrm{I}^{-} \longrightarrow\) (d) \(\mathrm{K}^{+}+\mathrm{HCO}_{3}^{-}+\mathrm{H}^{+}+\mathrm{NO}_{3}^{-} \longrightarrow\) (e) \(\mathrm{Mg}(\mathrm{s})+\mathrm{H}^{+} \longrightarrow\)

Step-by-Step Solution

Answer

(a) \( \mathrm{Ba}^{2+} + 2 \mathrm{OH}^{-} \longrightarrow \mathrm{Ba(OH)}_2 \) , (b) \( \mathrm{H}^{+} + \mathrm{Cl}^{-} \longrightarrow \mathrm{HCl} \) , (c) No reaction, (d) \( \mathrm{HCO}_{3}^{-} + \mathrm{H}^{+} \longrightarrow \mathrm{H}_{2} \mathrm{CO}_{3} \) , (e) No reaction

Step 1: Analyzing and forming compound if possible (a)

In [A], Ba2+ attracts OH-, producing a precipitate of Ba(OH)2. Hence, the net ionic equation is: \( \mathrm{Ba}^{2+} + 2 \mathrm{OH}^{-} \longrightarrow \mathrm{Ba(OH)}_2 \)

Step 2: Analyzing and forming compound if possible (b)

In [B], Cl- and H+ combine to form the compound HCl. Therefore, the net ionic equation is: \( \mathrm{H}^{+} + \mathrm{Cl}^{-} \longrightarrow \mathrm{HCl} \)

Step 3: Analyzing and forming compound if possible (c)

In [C], the FeS does not combine with H+ and I-, thus there's no reaction occurring and no net ionic equation.

Step 4: Analyzing and forming compound if possible (d)

In [D], bicarbonate ion [HCO3-] reacts with H+ to form a common weakly acidic compound, carbonic acid [H2CO3]. Hence, the net ionic equation is: \( \mathrm{HCO}_{3}^{-} + \mathrm{H}^{+} \longrightarrow \mathrm{H}_{2} \mathrm{CO}_{3} \)

Step 5: Analyzing and forming compound if possible (e)

Rounding up in [E], a solid like Mg cannot form new compounds with ions unless it ionizes into Mg2+. This reaction is impossible unless in the right conditions, thus we have to say there's no reaction taking place.

Key Concepts

Acid-Base Reactions

Acid-base reactions are a type of chemical reaction that occurs between an acid and a base. The primary goal is often the neutralization of the acid and base to produce water and a salt. When writing these reactions as net ionic equations, we focus on the species that actually change during the reaction, leaving out the spectator ions that do not participate directly in the reaction.
In the example from our exercise, consider the acid (\( ext{CH}_3 ext{COOH}\)) and the base (\( ext{OH}^-\)). An acid-base reaction occurs when the hydroxide ions (\( ext{OH}^- \)) from the base react with the hydrogen ions (\( ext{H}^+\)) from the acetic acid to form water (\( ext{H}_2 ext{O} \)).

• The acid donates a proton (\( ext{H}^+\)).
• The base accepts this proton, usually forming water.
• The resulting compound from the remaining ions can form a salt, depending on the strength of the acid and base.

Understanding this mechanism requires not only writing chemical formulas but recognizing the roles of acids and bases. This fundamental reaction is central to many biochemical and industrial processes.

Precipitation Reactions

Precipitation reactions occur when two solutions containing soluble salts are mixed, resulting in the formation of an insoluble product, or precipitate. In net ionic equations, the focus is on the ions that combine to form the precipitate.
For instance, in our problem, \( ext{Ba}^{2+} \) and \( ext{OH}^- \) ions combine to form barium hydroxide \( ext{Ba(OH)}_2 \), a common precipitate. The net ionic equation simplifies to only showing the species forming the solid:

• \( ext{Ba}^{2+} + 2 ext{OH}^- ightarrow ext{Ba(OH)}_2 ext{ (s)} \)

To correctly predict precipitation, understand the solubility rules, which dictate whether the compounds formed will remain in solution or form a precipitate. Remember:

• Sulfates and carbonates often form precipitates.
• Chlorides and bromides generally do not form precipitates unless combined with specific cations (like silver or lead).

Identifying when a precipitation reaction occurs helps in predicting the outcome of mixing different ionic compounds.

No Reaction Criteria

Sometimes, a combination of substances results in no reaction. This may occur for several reasons in a chemical context.
For instance, the lack of reaction in the equation with \( ext{FeS} \) illustrates these points. In the original question, \( ext{FeS} \), \( ext{H}^+ \), and \( ext{I}^- \) do not react to form a new compound.

• The elements and ions might not have a sufficient driving force to form a new product.
• No more favorable products are formed by combining the given ions.
• Solid metals or salts may not react if they are unreactive in the given conditions.

Hence, it’s important to consider the reactivity and solubility of substances involved, as well as the conditions provided during the reaction. By understanding the behavior of compounds and ions in a solution, you can better predict when a reaction may or may not occur.