Understanding the Reaction
Halides (like chloride, bromide, and iodide ions) react with silver nitrate (AgNO₃) to produce a precipitate of silver halide (AgX, where X is the halide) and a soluble nitrate salt.
General Ionic Equation
The general ionic equation for this reaction is:
Ag⁺(aq) + X⁻(aq) → AgX(s)
Specific Examples
* Silver Chloride (AgCl)
* Molecular Equation: AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq)
* Ionic Equation: Ag⁺(aq) + NO₃⁻(aq) + Na⁺(aq) + Cl⁻(aq) → AgCl(s) + Na⁺(aq) + NO₃⁻(aq)
* Net Ionic Equation: Ag⁺(aq) + Cl⁻(aq) → AgCl(s)
* Silver Bromide (AgBr)
* Molecular Equation: AgNO₃(aq) + KBr(aq) → AgBr(s) + KNO₃(aq)
* Ionic Equation: Ag⁺(aq) + NO₃⁻(aq) + K⁺(aq) + Br⁻(aq) → AgBr(s) + K⁺(aq) + NO₃⁻(aq)
* Net Ionic Equation: Ag⁺(aq) + Br⁻(aq) → AgBr(s)
* Silver Iodide (AgI)
* Molecular Equation: AgNO₃(aq) + NaI(aq) → AgI(s) + NaNO₃(aq)
* Ionic Equation: Ag⁺(aq) + NO₃⁻(aq) + Na⁺(aq) + I⁻(aq) → AgI(s) + Na⁺(aq) + NO₃⁻(aq)
* Net Ionic Equation: Ag⁺(aq) + I⁻(aq) → AgI(s)
Key Points
* Spectator Ions: In the ionic equation, the ions that appear on both sides of the equation (like Na⁺ and NO₃⁻ in the examples) are called spectator ions. They do not participate in the actual precipitation reaction.
* Net Ionic Equation: The net ionic equation only includes the ions that directly react to form the precipitate. This provides a more concise representation of the reaction.
* Solubility: The solubility of silver halides decreases down the group (AgCl > AgBr > AgI). This means silver iodide is the least soluble and forms the most readily visible precipitate.
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