Question

Write a chemical equation for the reaction of aqueous solutions of lithium iodide and silver nitrate to give silver iodide precipitate and aqueous lithium nitrate.

Short answer

The balanced equation is \[ \text{LiI (aq)} + \text{AgNO}_3 \text{(aq)} \rightarrow \text{AgI (s)} + \text{LiNO}_3 \text{(aq)} \].

Step-by-step solution

Identify Reactants and Products

The reactants in this reaction are lithium iodide \( \text{LiI} \), and silver nitrate \( \text{AgNO}_3 \). The products formed are silver iodide, \( \text{AgI} \) (a precipitate), and lithium nitrate \( \text{LiNO}_3 \).

Write Chemical Formulas for the Compounds

List the formulas for each reactant and product: Reactants: \( \text{LiI} \), and \( \text{AgNO}_3 \). Products: \( \text{AgI} \), and \( \text{LiNO}_3 \).

Arrange Reactants and Products in Equation Form

Write out the unbalanced chemical equation by placing the reactants on the left and the products on the right using chemical formulas: \[ \text{LiI} + \text{AgNO}_3 \rightarrow \text{AgI} + \text{LiNO}_3 \]

Balance the Chemical Equation

Check if the equation is balanced by counting the atoms of each element: - Li: 1 reactant, 1 product - I: 1 reactant, 1 product - Ag: 1 reactant, 1 product - NO\(_3\): 1 reactant, 1 product Since there are equal numbers of each type of atom on both sides, the equation is already balanced.

Include State Symbols

Add the state of each compound: - \( \text{LiI (aq)} \): aqueous - \( \text{AgNO}_3 \text{(aq)} \): aqueous - \( \text{AgI (s)} \): solid (precipitate) - \( \text{LiNO}_3 \text{(aq)} \): aqueous, The full balanced equation with state symbols is: \[ \text{LiI (aq)} + \text{AgNO}_3 \text{(aq)} \rightarrow \text{AgI (s)} + \text{LiNO}_3 \text{(aq)} \]

Key concepts

Balancing Chemical Equations

Balancing chemical equations is an essential skill in chemistry. It's like balancing a see-saw; both sides must have equal weight. Here, it means the numbers and types of atoms must be the same on both sides of the equation. This is done to follow the Law of Conservation of Mass.
The law states that matter cannot be created or destroyed in a chemical reaction. To balance an equation:

• First, write down all the reactants and products with their chemical formulas.
• Next, count the number of atoms of each element in both the reactants and the products.
• Ensure the number of each type of atom is equal on both sides by adjusting coefficients (the numbers in front of compounds).

In the given exercise, this wasn't necessary since the initial equation was already balanced. This might not always be the case, so it's a good step to double-check!

Precipitation Reactions

Precipitation reactions are a type of chemical reaction where two soluble substances in aqueous solutions combine to form an insoluble solid, known as a precipitate.
These reactions involve ionic compounds. When the ions in the solutions mix, if any combination of cation and anion is insoluble in water, it will form a solid precipitate. For example:

• When lithium iodide (\( \text{LiI} \)) and silver nitrate (\( \text{AgNO}_3 \)) react, they exchange partners to form silver iodide (\( \text{AgI} \)), which is not soluble in water, hence precipitating out.
• The product formed, silver iodide, appears as a cloudy solid in the solution due to its insolubility.

The formation of a precipitate is often used as evidence that a chemical reaction has occurred. Understanding which compounds will precipitate requires knowledge of solubility rules.

Aqueous Solutions

Aqueous solutions are solutions in which water is the solvent. Water, being a universal solvent, dissolves many substances due to its polar nature. This makes it an excellent medium for reactions.
In chemistry, the term "aqueous" is denoted by (aq) after the chemical formula, indicating that the compound is dissolved in water. For example:

• \( \text{LiI (aq)} \) means lithium iodide is dissolved in water.
• \( \text{AgNO}_3 \text{ (aq)} \) means silver nitrate is also in an aqueous solution.

When reactants are in aqueous solutions, they become more accessible for ions to collide and interact, increasing the likelihood of reactions. Proper notation of the state of substances in a balanced equation provides critical information about the conditions under which the reaction occurs, like solubility and physical states.