How is a net ionic equation written from a complete ionic equation?
A. The ions are combined to form compounds.
B. The (aq) state symbols are removed.
C. The spectator ions are removed.
D. Alions are removed from the equation.
The Correct Answer and Explanation is:
The correct answer is C. The spectator ions are removed.
Explanation
To understand how to write a net ionic equation from a complete ionic equation, it is essential to grasp the roles of different ions in a chemical reaction. When a reaction occurs in aqueous solution, compounds that dissociate into ions are represented in their ionic form. A complete ionic equation lists all the ions present in the solution, including those that do not participate in the actual chemical reaction. These non-participating ions are termed “spectator ions.”
The process of deriving a net ionic equation involves the following steps:
- Start with the Complete Ionic Equation: This equation shows all the ions present in the solution. For example, consider the reaction between sodium chloride (NaCl) and silver nitrate (AgNO₃):
[
\text{Na}^+ (aq) + \text{Cl}^- (aq) + \text{Ag}^+ (aq) + \text{NO}_3^- (aq) \rightarrow \text{Na}^+ (aq) + \text{NO}_3^- (aq) + \text{AgCl} (s)
]
Here, Na⁺ and NO₃⁻ are spectator ions because they do not undergo any change during the reaction. - Identify Spectator Ions: Determine which ions do not participate in the reaction. In our example, Na⁺ and NO₃⁻ are present on both sides of the equation and do not change; they are spectators.
- Remove Spectator Ions: To form the net ionic equation, remove the spectator ions from the complete ionic equation. This results in:
[
\text{Ag}^+ (aq) + \text{Cl}^- (aq) \rightarrow \text{AgCl} (s)
]
This net ionic equation now focuses solely on the species that participate in the reaction, illustrating the formation of the insoluble precipitate AgCl. - Check for Correctness: Ensure that the remaining equation is balanced and accurately represents the chemical process occurring in the solution.
By removing the spectator ions, the net ionic equation emphasizes the actual chemical change, providing a clearer understanding of the reaction dynamics. This approach is particularly useful in analyzing precipitation reactions, acid-base reactions, and redox processes, helping chemists focus on the essential components that are involved in the reaction.