Question

Write a balanced equation for the dissociation of each of the following strong electrolytes in water: a. \(\mathrm{KCl}\) b. \(\mathrm{CaCl}_{2}\) c. \(\mathrm{K}_{3} \mathrm{PO}_{4}\) d. \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{3}\)

Short answer

a. \( \mathrm{KCl} \rightarrow \mathrm{K}^{+} + \mathrm{Cl}^{-} \); b. \( \mathrm{CaCl}_{2} \rightarrow \mathrm{Ca}^{2+} + 2\mathrm{Cl}^{-} \); c. \( \mathrm{K}_{3} \mathrm{PO}_{4} \rightarrow 3 \mathrm{K}^{+} + \mathrm{PO}_{4}^{3-} \); d. \( \mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{3} \rightarrow \mathrm{Fe}^{3+} + 3 \mathrm{NO}_{3}^{-} \)

Step-by-step solution

Identify the compound

First, identify the compound for which the dissociation equation will be written.

Write the general form of dissociation

Write the general form of the dissociation for strong electrolytes. Strong electrolytes completely dissociate into their ions in water.

Balance the dissociation equation

Ensure that the equation has the same number of each type of atom on both the reactant and product sides. This ensures the charge is balanced.

Dissociation of KCl

For \( \mathrm{KCl} \), the dissociation in water is: \[ \mathrm{KCl} (\mathrm{aq}) \rightarrow \mathrm{K}^{+} (\mathrm{aq}) + \mathrm{Cl}^{-} (\mathrm{aq}) \]

Dissociation of CaCl2

For \( \mathrm{CaCl}_{2} \), the dissociation in water is: \[ \mathrm{CaCl}_{2} (\mathrm{aq}) \rightarrow \mathrm{Ca}^{2+} (\mathrm{aq}) + 2\mathrm{Cl}^{-} (\mathrm{aq}) \]

Dissociation of K3PO4

For \( \mathrm{K}_{3} \mathrm{PO}_{4} \), the dissociation in water is: \[ \mathrm{K}_{3} \mathrm{PO}_{4} (\mathrm{aq}) \rightarrow 3 \mathrm{K}^{+} (\mathrm{aq}) + \mathrm{PO}_{4}^{3-} (\mathrm{aq}) \]

Dissociation of Fe(NO3)3

For \( \mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{3} \), the dissociation in water is: \[ \mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{3} (\mathrm{aq}) \rightarrow \mathrm{Fe}^{3+} (\mathrm{aq}) + 3 \mathrm{NO}_{3}^{-} (\mathrm{aq}) \]

Key concepts

strong electrolytes

Strong electrolytes are substances that completely dissociate into ions when dissolved in water. This means they break apart into their positive and negative ions.
Examples include salts like potassium chloride (KCl), calcium chloride (CaCl₂), and acids like hydrochloric acid (HCl).
When these compounds dissolve, their ions freely move in the solution, allowing it to conduct electricity very well.
This complete dissociation is a key feature of strong electrolytes, making them different from weak electrolytes, which only partially dissociate.

aqueous solutions

An aqueous solution is a solution in which the solvent is water. It's a term you'll see often in chemistry.
When a solid, liquid, or gas dissolves in water, it forms an aqueous solution, represented as (aq) in chemical equations.
For example, when potassium chloride (KCl) dissolves in water, it forms an aqueous solution of K⁺ and Cl⁻ ions.
Understanding aqueous solutions is important because many chemical reactions, including ion dissociation, occur in this medium.

balanced chemical equations

In chemistry, a balanced chemical equation ensures that the number of atoms for each element is the same on both sides of the equation.
This reflects the Law of Conservation of Mass, which states that matter cannot be created or destroyed in a chemical reaction.
For instance, the dissociation of calcium chloride (CaCl₂) is balanced as:
\[ \text{CaCl}_2(\text{aq}) \rightarrow \text{Ca}^{2+}(\text{aq}) + 2\text{Cl}^-(\text{aq}) \]
Here, we have one calcium atom and two chlorine atoms on both sides, keeping the equation balanced.
Balancing equations is crucial because it accurate chemical reactions and ensures the stoichiometry is correct.

ion dissociation

Ion dissociation is the process by which an ionic compound separates into its constituent ions when dissolved in water.
For strong electrolytes, this dissociation is complete. For example, dissociation of \[ \text{KCl}(\text{aq}) \rightarrow \text{K}^+(\text{aq}) + \text{Cl}^-(\text{aq}) \]
This means that every KCl molecule splits into one potassium ion (K⁺) and one chloride ion (Cl⁻).
Understanding ion dissociation helps predict the behavior of substances in solution, such as conductivity and reactivity.
Different compounds will dissociate differently based on their chemical makeup, and balancing these dissociations is important for accurate scientific work.