<< Chapter < Page Chapter >> Page >

Types of reactions

We will look at three types of reactions that occur in aqueous solutions. These are precipitation reactions, acid-base reactions and redox reactions. Precipitation and acid-base reactions are sometimes called ion exchange reactions. Redox reactions are electron transfer reactions. It is important to remember the difference between these two types of reactions. In ion exchange reactions ions are exchanged, in electron transfer reactions electrons are transferred. These terms will be explained further in the following sections.

Ion exchange reactions can be represented by:

AB(aq) + CD(aq) AD + CB
Either AD or CB may be a solid or a gas. When a solid forms this is known as a precipitation reaction. If a gas is formed then this may be called a gas forming reaction. Acid-base reactions are a special class of ion exchange reactions and we will look at them seperately.

The formation of a precipitate or a gas helps to make the reaction happen. We say that the reaction is driven by the formation of a precipitate or a gas. All chemical reactions will only take place if there is something to make them happen. For some reactions this happens easily and for others it is harder to make the reaction occur.

Ion exchange reaction
A type of reaction where the positive ions exchange their respective negative ions due to a driving force.

Interesting fact

Ion exchange reactions are used in ion exchange chromatography. Ion exchange chromatography is used to purify water and as a means of softening water. Often when chemists talk about ion exchange, they mean ion exchange chromatography.

Precipitation reactions

Sometimes, ions in solution may react with each other to form a new substance that is insoluble . This is called a precipitate .

A precipitate is the solid that forms in a solution during a chemical reaction.

Demonstration : the reaction of ions in solution

Apparatus and materials:

4 test tubes; copper(II) chloride solution; sodium carbonate solution; sodium sulphate solution


  1. Prepare 2 test tubes with approximately 5 ml of dilute Cu(II) chloride solution in each
  2. Prepare 1 test tube with 5 ml sodium carbonate solution
  3. Prepare 1 test tube with 5 ml sodium sulphate solution
  4. Carefully pour the sodium carbonate solution into one of the test tubes containing copper(II) chloride and observe what happens
  5. Carefully pour the sodium sulphate solution into the second test tube containing copper(II) chloride and observe what happens


  1. A light blue precipitate forms when sodium carbonate reacts with copper(II) chloride
  2. No precipitate forms when sodium sulphate reacts with copper(II) chloride

It is important to understand what happened in the previous demonstration. We will look at what happens in each reaction, step by step.

  1. Reaction 1: Sodium carbonate reacts with copper(II) chloride.
    When these compounds react, a number of ions are present in solution: Cu 2 + , Cl - , Na + and CO 3 2 - . Because there are lots of ions in solution, they will collide with each other and may recombine in different ways. The product that forms may be insoluble, in whichcase a precipitate will form, or the product will be soluble, in which case the ions will go back into solution. Let's see how the ions in this example could have combined with each other:
    Cu 2 + + CO 3 2 - CuCO 3
    Cu 2 + + 2 Cl - CuCl 2
    Na + + Cl - NaCl
    2 Na + + CO 3 2 - Na 2 CO 3
    You can automatically exclude the reactions where sodium carbonate and copper(II) chloride are the products because these were the initial reactants. You also know that sodium chloride ( NaCl ) is soluble in water, so the remaining product (copper carbonate) must be the one that is insoluble. It is also possible to look up which salts are soluble and which are insoluble. If you do this, you will find that most carbonates are insoluble, therefore the precipitate that forms in this reaction must be CuCO 3 . The reaction that has taken place between the ions in solution is as follows:
    2 Na + + CO 3 2 - + Cu 2 + + 2 Cl - CuCO 3 + 2 Na + + 2 Cl -
  2. Reaction 2: Sodium sulphate reacts with copper(II) chloride.
    The ions that are present in solution are Cu 2 + , Cl - , Na + and SO 4 2 - . The ions collide with each other and may recombine in different ways. The possible combinations of the ions are as follows:
    Cu 2 + + SO 4 2 - CuSO 4
    Cu 2 + + 2 Cl - CuCl 2
    Na + + Cl - NaCl
    Na + + SO 4 2 - Na 2 SO 4
    If we look up which of these salts are soluble and which are insoluble, we see that most chlorides and most sulphates are soluble. This is why no precipitate forms in this second reaction. Even when the ions recombine, they immediately separate and go back into solution. The reaction that has taken place between the ions in solution is as follows:
    2 Na + + SO 4 2 - + Cu 2 + + 2 Cl - 2 Na + + SO 4 2 - + Cu 2 + + 2 Cl -

Questions & Answers

are nano particles real
Missy Reply
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
Lale Reply
no can't
where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
has a lot of application modern world
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Richard is sitting on his chair and reading a newspaper three (3) meters away from the door
Jeo Reply
The fundamental frequency of a sonometer wire streached by a load of relative density 's'are n¹ and n² when the load is in air and completly immersed in water respectively then the lation n²/na is
Mukesh Reply
Properties of longitudinal waves
Sharoon Reply

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now

Source:  OpenStax, Siyavula textbooks: grade 10 physical science [caps]. OpenStax CNX. Sep 30, 2011 Download for free at http://cnx.org/content/col11305/1.7
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Siyavula textbooks: grade 10 physical science [caps]' conversation and receive update notifications?