Double Displacement Examples in Chemistry

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Double Displacement.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Chemistry.

Concept Recap

A chemical reaction in which the positive ions (cations) of two ionic compounds in aqueous solution exchange partners, forming two new ionic compounds. The reaction is driven by the formation of a precipitate, a gas, or water.

Two couples swap partners at a dance — each positive ion pairs with the other's negative ion.

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How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Pattern: AB + CD → AD + CB. Typically driven by forming a precipitate, water, or gas.

Common stuck point: The reaction proceeds only if one product is insoluble (precipitate), a gas, or water — otherwise ions just stay mixed.

Sense of Study hint: When predicting double displacement products, swap the cations between the two compounds. First write out the cations and anions of each reactant separately. Then pair each cation with the other compound's anion, making sure charges balance in the new formulas. Finally, check solubility rules to determine if a precipitate forms — if neither product is insoluble, gaseous, or water, no reaction occurs.

Worked Examples

Example 1

easy
Write the balanced equation for the reaction between sodium chloride and silver nitrate solutions.

Solution

  1. 1
    Double displacement: \text{AB} + \text{CD} \rightarrow \text{AD} + \text{CB} (cations switch partners).
  2. 2
    \text{NaCl} + \text{AgNO}_3 \rightarrow \text{NaNO}_3 + \text{AgCl}.
  3. 3
    AgCl is insoluble (precipitate ↓). The equation is already balanced: 1 of each element on each side.

Answer

\text{NaCl} + \text{AgNO}_3 \rightarrow \text{NaNO}_3 + \text{AgCl}\downarrow
Double displacement (metathesis) reactions occur when the exchange of ions produces an insoluble precipitate, a gas, or water. Solubility rules help predict whether a precipitate will form.

Example 2

medium
Predict the products and write the balanced equation: \text{BaCl}_2 + \text{Na}_2\text{SO}_4 \rightarrow ?

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

easy
Classify: \text{HCl} + \text{NaOH} \rightarrow \text{NaCl} + \text{H}_2\text{O}.

Example 2

hard
When solutions of lead(II) nitrate and potassium iodide are mixed, a bright yellow precipitate forms. Write the balanced molecular equation, identify the precipitate, and explain how to predict which product is insoluble.
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Background Knowledge

These ideas may be useful before you work through the harder examples.

chemical reaction