Question

What are double decomposition reactions?

Answer 1

A double decomposition reaction is a reaction in which the positive ions and negative ions in two compounds 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 decomposition reactions 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 neutralization 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 double replacement reactions.