Title: 4. REACTION CLASSIFICATION 4.2 Double-replacement reaction
Course: Chemist€ry

4.2 Double-replacement reaction

A characteristic of a double-replacement equation is that there are two compounds as reactants and two different compounds as products. For instance,

KI (aq) + Pb(NO_3)_2(aq) → K(NO_3) (aq) + PbI_2 (s)

There is a couple exchange; the anions have exchanged their cations. Or, what is the same, the cations have exchanged their anions.

Example

Predict the products of this double-replacement equation:

CuCl_2(aq) + AgNO_3(aq) →  _________? + __________?

Solution

You can either switch the cations or switch the anions, we would expect the products to be Cu(NO_3)_2(aq) and AgCl(s)

Predicting whether a double-replacement reaction occurs is more difficult than predicting a single-replacement reaction. However, there is one type of double-replacement reaction that we can predict: the precipitation reaction.

LABPRACTICE 2, could be done by the teacher in class as a demonstration, check here video4

A precipitation reaction occurs when two ionic compounds are dissolved in water and form a new insoluble compound in water. This new compound turns into a solid precipitate. One of the driving force that makes the reaction occurs is the formation of a solid precipitate^5.

Video 4’:  from https://www.youtube.com/channel/UChL-dj4yhVmA7Gy_W4Nvx8w

5 - https://scholar.flatworldknowledge.com/