Question

Identify the spectator ions in the reaction between \(\mathrm{KCl}\) and \(\mathrm{AgNO}_{3}\) in an aqueous solution.

Short answer

The spectator ions are \( \text{K}^{+} \) and \( \text{NO}_{3}^{-} \).

Step-by-step solution

Write the balanced chemical equation

The first step is to write the balanced chemical equation for the reaction between \(\text{KCl}\) and \(\text{AgNO}_{3}\) in an aqueous solution. \[ \text{KCl} (aq) + \text{AgNO}_{3} (aq) \rightarrow \text{KNO}_{3} (aq) + \text{AgCl} (s) \] This represents the reaction where \(\text{K}\), \(\text{Cl}\), \(\text{Ag}\), and \(\text{NO}_{3}\) ions participate.

Write the complete ionic equation

Next, write the complete ionic equation by separating all aqueous compounds into their constituent ions. \[ \text{K}^{+} (aq) + \text{Cl}^{-} (aq) + \text{Ag}^{+} (aq) + \text{NO}_{3}^{-} (aq) \rightarrow \text{K}^{+} (aq) + \text{NO}_{3}^{-} (aq) + \text{AgCl} (s) \] This shows all the ions present in the solution.

Identify and cancel out the spectator ions

Spectator ions are those ions that do not participate in the actual chemical reaction and remain unchanged on both sides of the equation. In this case, \(\text{K}^{+}\) and \(\text{NO}_{3}^{-}\) are the spectator ions. They appear on both sides of the equation. Canceling them out, we get: \[ \text{Cl}^{-} (aq) + \text{Ag}^{+} (aq) \rightarrow \text{AgCl} (s) \]

Key concepts

ionic equations

Ionic equations are a way of showing the details of what happens in a chemical reaction
that involves ions in an aqueous solution.
Instead of writing the full molecular equations, we break down each aqueous substance into its ions.
For example, the full ionic equation for the reaction between potassium chloride (\( \text{KCl} \))
and silver nitrate (\( \text{AgNO}_3 \)) can be written as:
\[ \text{K}^+ (aq) + \text{Cl}^- (aq) + \text{Ag}^+ (aq) + \text{NO}_3^- (aq) \rightarrow \text{K}^+ (aq) + \text{NO}_3^- (aq) + \text{AgCl} (s) \]
This equation represents all the ions present in the reaction.
Breaking things down into ions helps us see which ions actually take part in the reaction and form a new substance.

chemical reactions

Chemical reactions are processes where substances (reactants) are transformed into different substances (products).
For a reaction to occur, reactants must interact in a way that breaking and forming of bonds result in new substances.
In our example with \( \text{KCl} \) and \( \text{AgNO}_3 \), a chemical reaction occurs to form \( \text{KNO}_3 \) and \( \text{AgCl} \).
Here, the reactants were \( \text{KCl} \) and \( \text{AgNO}_3 \), and the products are \( \text{KNO}_3 \) and \( \text{AgCl} \).
Chemical reactions can be represented by balanced chemical equations.

reactants and products

In any chemical reaction, the starting substances are called reactants, and the new substances formed are called products.
Taking the example given, we have:
- Reactants: \( \text{KCl} \) and \( \text{AgNO}_3 \)
- Products: \( \text{KNO}_3 \) and \( \text{AgCl} \)
In every balanced chemical equation, the number of atoms of each element is the same on both sides.
This conservation of mass is a key principle in chemistry.
The physical state of the reactants and products (solid, liquid, gas, aqueous) is also often included next to each compound in the equation.

precipitation reactions

Precipitation reactions occur when two aqueous solutions combine to form an insoluble solid called a precipitate.
In our given reaction between \( \text{KCl} \) and \( \text{AgNO}_3 \), \( \text{AgCl} \) is the precipitate.
Precipitates are identified by their solid state marker \((s)\) in the chemical equation.
Precipitation reactions are often used to isolate certain ions from a solution.
They are also an important tool in qualitative analysis to determine the presence of specific ions in a mixture.
Understanding how to identify and predict precipitates can be very useful in both laboratory settings and real-world applications.