What is a double-replacement reaction in chemistry?

Question

Henry Antrim · Accepted Answer

See explanation

Double replacement (sometimes referred to as double displacement) reactions are when parts of ionic compounds are switched to form two new ionic compounds.

Heres an image:

The way I think of it, since we're dealing with ionic compounds, is that when I write out a reaction I begin like this.

#color(green) (A^+)color(red)(B^-) + color(purple)(C^+)color(red)(D^-)->?+?#

We swap the anions so that #A# is now with #D# and #C# is now with #B# Visually,

#color(green) (A^+)color(red)(B^-) + color(purple)(C^+)color(red)(D^-)->color(green) (A^+)color(red)(D^-)+ color(purple)(C^+)color(red)(B^-)#

Heres an real example:

Say you have Sodium Cyanide and you react it with Hydrogen Bromide:

#color(green)(Na)color(red)(CN)_(aq) + color(purple)(H)color(red)(Br)_(aq)->?+?#

Well we have to remember what are the charges of cation and anion. Since this is an easy example, they all have a charge of +1 for the cations and -1 for the anions but we can just write #+ or -#

#color(green)(Na^+)color(red)(CN^-)_(aq) + color(purple)(H^+)color(red)(Br^-)_(aq)->?+?#

Next we can just switch the anions to get

#color(green)(Na^+)color(red)(CN^-)_(aq) + color(purple)(H^+)color(red)(Br^-)_(aq)->color(green)(Na^+)color(red)(Br^-)_(aq)+color(purple)(H^+)color(red)(CN^-)_(g)#

(This forms Hydrogen cyanide gas by the way)

I'm not the best at explaining chemistry so if this was confusing I apologize and recommend checking out Tyler DeWitt's video on "Types of Chemical Reactions" as well as the his videos.

Ellie Andrews · Answer

undefined a chemical process in which two substances trade ions to create two new substances.

Wyatt Adkins · Answer

undefined A double-replacement reaction, also known as a double-displacement reaction or metathesis reaction, is a chemical reaction where two compounds exchange ions to form two new compounds. In this reaction, the cations and anions of two compounds switch places to form two new compounds. The general form of a double-replacement reaction can be represented as:

$$ AB + CD \rightarrow AD + CB $$

In this reaction, compound AB reacts with compound CD to form compounds AD and CB. A key characteristic of double-replacement reactions is that there is no change in oxidation state of the elements involved. Double-replacement reactions often occur in aqueous solutions where the ions are free to move and interact with one another. Examples of double-replacement reactions include precipitation reactions, acid-base neutralization reactions, and gas formation reactions.