A double decomposition reaction is a reaction in which the positive ions and negative ions in two switch partners to form two new compounds.

The equation is often written in the general form

##”AB + CD” → “CB + AD”##

The older term double decomposition has been largely replaced by the terms double displacement, double replacement, and metathesis.

Many double are precipitation reactions.

##color(blue)(“Ag”)color(red)(“NO”_3)”(aq)” + color(orange)(“Na”) color(green)(“Cl”)”(aq)” → color(blue)(“Ag”) color(teal)(“Cl”)”(s)” + color(orange)(“Na”) color(red)(“NO”_3)”(aq)”##

Others are acid-base reactions.

## color(blue)(“H”)color(red)(“Cl”)”(aq)” + color(orange)(“Na”) color(green)(“OH”)”(aq)”→ color(orange)(“Na”)color(red)(“Cl”)”(aq)” + color(blue)(“H”) color(green)(“OH”)”(l)”##

Here is a good video on .