Question

Show how each of the following strong electrolytes “breaks up” into its component ions upon dissolving in water by drawing molecular-level pictures. a. NaBr f. \({FeSO}_{4}\) b. \({MgCl}_{2}\) g. \({KMnO}_{4}\) c. \({Al}({NO}_{3})_{3}\) h. \({HClO}_{4}\) d. \(({NH}_{4})_{2} {SO}_{4}\) i. \({NH}_{4} {C}_{2} {H}_{3} {O}_{2}\) (ammonium acetate) e. \({NaOH}\)

Short answer

a. NaBr \(\longrightarrow\) Na⁺ + Br⁻ b. \({MgCl}_{2}\) \(\longrightarrow\) Mg²⁺ + 2Cl⁻ c. \({Al}({NO}_{3})_{3}\) \(\longrightarrow\) Al³⁺ + 3\({NO}_{3}⁻\) d. \(({NH}_{4})_{2} {SO}_{4}\) \(\longrightarrow\) 2\({NH}_{4}⁺\) + \({SO}_{4}²⁻\) e. \({NaOH}\) \(\longrightarrow\) Na⁺ + OH⁻ f. \({FeSO}_{4}\) \(\longrightarrow\) Fe²⁺ + \({SO}_{4}²⁻\) g. \({KMnO}_{4}\) \(\longrightarrow\) K⁺ + \({MnO}_{4}⁻\) h. \({HClO}_{4}\) \(\longrightarrow\) H⁺ + \({ClO}_{4}⁻\) i. \({NH}_{4} {C}_{2} {H}_{3} {O}_{2}\) \(\longrightarrow\) \({NH}_{4}⁺\) + \({C}_{2} {H}_{3} {O}_{2}⁻\)

Step-by-step solution

a. NaBr dissociation

Sodium bromide (NaBr) dissociates into the sodium ion (Na⁺) and the bromide ion (Br⁻). Upon dissolving in water, the formula can be written as: NaBr \(\longrightarrow\) Na⁺ + Br⁻

b. \({MgCl}_{2}\) dissociation

Magnesium chloride (\({MgCl}_{2}\)) dissociates into the magnesium ion (Mg²⁺) and two chloride ions (2Cl⁻). Upon dissolving in water, the formula can be written as: \({MgCl}_{2}\) \(\longrightarrow\) Mg²⁺ + 2Cl⁻

c. \({Al}({NO}_{3})_{3}\) dissociation

Aluminum nitrate (\({Al}({NO}_{3})_{3}\)) dissociates into the aluminum ion (Al³⁺) and three nitrate ions (3\({NO}_{3}⁻\)). Upon dissolving in water, the formula can be written as: \({Al}({NO}_{3})_{3}\) \(\longrightarrow\) Al³⁺ + 3\({NO}_{3}⁻\)

d. \(({NH}_{4})_{2} {SO}_{4}\) dissociation

Ammonium sulfate (\(({NH}_{4})_{2} {SO}_{4}\)) dissociates into two ammonium ions (2\({NH}_{4}⁺\)) and one sulfate ion (\({SO}_{4}²⁻\)). Upon dissolving in water, the formula can be written as: \(({NH}_{4})_{2} {SO}_{4}\) \(\longrightarrow\) 2\({NH}_{4}⁺\) + \({SO}_{4}²⁻\)

e. \({NaOH}\) dissociation

Sodium hydroxide (\({NaOH}\)) dissociates into the sodium ion (Na⁺) and the hydroxide ion (OH⁻). Upon dissolving in water, the formula can be written as: \({NaOH}\) \(\longrightarrow\) Na⁺ + OH⁻

f. \({FeSO}_{4}\) dissociation

Iron(II) sulfate (\({FeSO}_{4}\)) dissociates into the iron(II) ion (Fe²⁺) and the sulfate ion (\({SO}_{4}²⁻\)). Upon dissolving in water, the formula can be written as: \({FeSO}_{4}\) \(\longrightarrow\) Fe²⁺ + \({SO}_{4}²⁻\)

g. \({KMnO}_{4}\) dissociation

Potassium permanganate (\({KMnO}_{4}\)) dissociates into the potassium ion (K⁺) and the permanganate ion (\({MnO}_{4}⁻\)). Upon dissolving in water, the formula can be written as: \({KMnO}_{4}\) \(\longrightarrow\) K⁺ + \({MnO}_{4}⁻\)

h. \({HClO}_{4}\) dissociation

Perchloric acid (\({HClO}_{4}\)) dissociates into the hydrogen ion (H⁺) and the perchlorate ion (\({ClO}_{4}⁻\)). Upon dissolving in water, the formula can be written as: \({HClO}_{4}\) \(\longrightarrow\) H⁺ + \({ClO}_{4}⁻\)

i. \({NH}_{4} {C}_{2} {H}_{3} {O}_{2}\) dissociation

Ammonium acetate (\({NH}_{4} {C}_{2} {H}_{3} {O}_{2}\)) dissociates into the ammonium ion (\({NH}_{4}⁺\)) and the acetate ion (\({C}_{2} {H}_{3} {O}_{2}⁻\)). Upon dissolving in water, the formula can be written as: \({NH}_{4} {C}_{2} {H}_{3} {O}_{2}\) \(\longrightarrow\) \({NH}_{4}⁺\) + \({C}_{2} {H}_{3} {O}_{2}⁻}\)

Key concepts

Ion Dissociation

When strong electrolytes dissolve in water, they undergo a process called ion dissociation. This means that the compound breaks down into its component ions. This is because water molecules are highly polar, meaning they have a positive side and a negative side. This polarity allows water to surround the ions, separating them and keeping them evenly dispersed within the solution.

Let's consider sodium bromide (NaBr). It dissociates into sodium ions (Na⁺) and bromide ions (Br⁻) when it is added to water. The interaction with water molecules results in the formula: \[\text{NaBr} \longrightarrow \text{Na}^+ + \text{Br}^-\]This principle applies to all strong electrolytes, like magnesium chloride (MgCl₂), which dissociates into one magnesium ion (Mg²⁺) and two chloride ions (Cl⁻):\[\text{MgCl}_2 \longrightarrow \text{Mg}^{2+} + 2\text{Cl}^-\]This process is crucial for understanding how solutions conduct electricity. The free movement of ions in water carries electric current, which makes solutions made from strong electrolytes excellent conductors.

Aqueous Solution

An aqueous solution is a solution in which water is the solvent. When ionic compounds dissolve in water, they form aqueous solutions by dissociating into individual ions. This is significant because it means that the original compound's structure is broken down and the ions interact independently with the water molecules.

For example, when aluminum nitrate (Al(NO₃)₃) dissolves, it yields aluminum ions (Al³⁺) and nitrate ions (NO₃⁻) in the solution.

• Aluminum nitrate in water will dissociate like this:\[\text{Al}(\text{NO}_3)_3 \longrightarrow \text{Al}^{3+} + 3\text{NO}_3^-\]
• This means that each aluminum ion is surrounded by water molecules, stabilizing it in the solution.

Aqueous solutions are not limited to salts. They can also include acids, such as perchloric acid (HClO₄), which dissociates into hydrogen ions (H⁺) and perchlorate ions (ClO₄⁻).\[\text{HClO}_4 \longrightarrow \text{H}^+ + \text{ClO}_4^-\]In both cases, water's role is vital for separating and keeping ions throughout the solution, enabling various chemical processes.

Chemical Equations

Chemical equations are a concise way of showing what happens in a chemical reaction, including ion dissociation. These equations use formulas and symbols to depict the substances involved and what they change into.

In the context of ion dissociation, equations show how a solid compound separates into individual ions when it is dissolved in water. For instance, look at ammonium sulfate ((NH₄)₂SO₄) when it dissociates:\[(\text{NH}_4)_2\text{SO}_4 \longrightarrow 2\text{NH}_4^+ + \text{SO}_4^{2-}\]The chemical equation indicates that two ammonium ions are created for each sulfate ion when this compound dissolves.

• These equations guarantee that the balance of charge is maintained, meaning the number of positive and negative charges is equal on both sides.

The beauty of chemical equations is in their ability to communicate complex reactions in a straightforward manner, helping us to better understand processes such as the dissociation of electrolytes like ammonium acetate (NH₄C₂H₃O₂):\[\text{NH}_4\text{C}_2\text{H}_3\text{O}_2 \longrightarrow \text{NH}_4^+ + \text{C}_2\text{H}_3\text{O}_2^-\]This clear depiction is indispensable for studying and predicting the behavior of chemical substances in various conditions.