DoubleReplacement

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Double Replacement Reaction Notes

Double Replacement reactions are reactions where two ionic compounds dissolved in water (i.e. there are both aqueous substances). In this type of reaction the cations (or anions) switch places to form two new compounds. The general form is:

                                     compound  +  compound  ->  compound + compound

                                         AB    +     CD     ->     AD    +    CB

A double replacement reaction will not always occur. For a reaction to occur, at least one of the following must be a product:
a. A solid is formed (called a precipitate). Click here for direction, Double Replacement - Solid Formed
b. Water is formed (actually the more correct answer is a liquid. However, we really only use one liquid in 1st year chem, water) Click here for directions, Double Replacement Rxn - Neutralization Rxn
c. A gas formed. Click here for directions, Double Replacement - Gas Formed
Examples:

NaCl(aq) + Ag(NO₃) -> Na(NO₃)(aq) + AgCl(s)
(NH₄)₃(PO₄)(aq) + AlCl₃(aq) -> (NH₄)Cl(aq) + Al(PO₄)(s)