In this blog, we will learn about different types of chemical reactions with examples. You must have often seen during whitewashing in your house, workers mixing lime (chuna) with water. The mixture becomes hot and steam starts coming out. You also must be observed that while tasting glucose, your tongue gets a sensation of cold.
You must have seen iron getting rusted. All these are examples of chemical reactions because some new substances are formed in all of them.
So, In a chemical reaction, the substances known as reactants are converted into new substances called products. But, are all the chemical reactions the same? or there exist different categories of chemical reactions. In fact, chemical reactions are of different types and in this module, we will learn about them.
Different types of chemical reactions are:
- Combination reaction
- Decomposition reaction
- Displacement reaction
- Double displacement reaction
- Oxidation and reduction reaction
Let us learn about all the types of chemical reactions with examples in detail below.
1. Combination reaction
Let us take a small amount of CaO (calcium oxide) in a beaker and slowly add water to it. CaO reacts vigorously with water to produce slaked lime and releases a large amount of heat.
On touching the beaker, you can easily feel that the beaker has become hot. In this reaction, CaO and H2O combine to form a single product that is Ca(OH)2. Such reactions, in which two or more substances combine to form a single substance, are called combination reactions.
An example of a combination reaction is when Carbon (coal) burns in the air to form carbon dioxide. In this reaction two elements, carbon and oxygen are combined together to form a single compound, carbon dioxide.
Another example of a combination reaction is the formation of water. Hydrogen burns in oxygen to form water. In this reaction, two elements hydrogen and oxygen are combined together to form a single compound, water.
Let us learn about more types of chemical reactions.
2. Decomposition Reactions (M)
Let us take about 2 gms of FeSO4 (Ferrous Sulphate crystals ) in a test tube. Hold it with a test tube holder and heat it over the flame of a burner. What do you observe?
The green color of ferrous sulfate crystals changes to white and then a brown solid is formed (which is ferric oxide) and a colorless gas having the smell of sulfur evolves out of the boiling tube.
In fact, the ferrous sulfate crystals (FeSO4.7H2O) lose water when heated to form anhydrous ferrous sulfate, which is white in color. It then decomposes to ferric oxide (Fe2O3), sulfur dioxide (SO2), and Sulphur trioxide (SO3).
Such a reaction in which a single reactant breaks down to give a simpler product is called a decomposition reaction. It is important to note that when a decomposition reaction is carried out by heating, it is called thermal decomposition.
Some other examples of decomposition reactions are when calcium carbonate is heated, it decomposes to give calcium oxide and carbon dioxide. When lead nitrate powder is heated, lead monoxide is formed along with the brown fumes of nitrogen dioxide and colorless oxygen gas.
Similarly, when we decompose water using an electric current, oxygen gas is collected at the anode and hydrogen gas at the cathode.
If white silver chloride is kept under the sun in a china dish, it decomposes to form silver metal and chlorine gas by the action of light. Silver bromide which is used in black and white photography also decomposes into silver metal and bromine vapors.
Keep reading to discover 3 more types of chemical reactions.
3. Displacement reaction:
Take a few iron nails and put them in a test tube, containing blue copper sulfate solution. What do you observe?
After some time, the iron nails become brownish in color and the blue color of the copper sulfate solution fades. In fact, in this reaction, iron which is more reactive than copper has displaced or removed copper from the copper sulfate solution.
Such a reaction in which a more reactive element displaces a less reactive element from the solution is called a displacement reaction.
Other examples of displacement reactions are �
When zinc granules are placed in copper sulfate solution, zinc displaces copper from the copper sulfate compound and as a result, the copper is set free. The blue color of copper sulfate solution fades due to the formation of colorless zinc sulfate.
A reddish-brown deposit of copper metal is formed on the zinc granules. This displacement reaction takes place because zinc is more reactive than copper.
4. Double displacement reaction
Take a colorless solution of sodium sulfate in a test tube and add colourless solution of barium chloride to it. What do you observe? Some white-colored insoluble substance is formed.
Yes, when sodium sulfate and barium chloride reacts, soluble sodium chloride and insoluble barium sulfate are formed. In this reaction, barium sulfate is formed as a white insoluble solid called precipitate.
Here the exchange of ions takes place. Such reactions in which the exchange of ions between the reactants takes place to form two new compounds are called double displacement reactions.
Another example of a double displacement reaction is the reaction of lead nitrate and potassium iodide, in which a yellow precipitate of lead iodide and soluble potassium nitrate is formed.
The insoluble barium sulfate and lead iodide are formed as precipitates. Any reaction in which an insoluble solid (called precipitate) is formed that separates from the solution is called a precipitation reaction.
5. Oxidation and reduction reaction
Let us take the copper powder into a china dish and heat it. What do you observe?
Black powder of copper oxide
As oxygen is added to copper, it is called an oxidation reaction. Such reactions where either oxygen is added or hydrogen is removed are called oxidation reactions.
Now if we pass Hydrogen gas over the heated copper oxide, the black coating on the surface turns brown as oxygen is removed from copper oxide & copper is obtained again.
Such a reaction in which either Hydrogen is added or oxygen is removed is called reduction.
In this reaction, we see that oxidation & reduction takes place together. The oxidation and reduction reactions are also called redox reactions. The substance which gains oxygen during a reaction is said to be oxidized and the substance which gives oxygen or removes hydrogen for oxidation is called an oxidizing agent.
The substance that losses oxygen during a reaction or gains Hydrogen is said to be reduced and a substance that gives hydrogen or removes oxygen is called a reducing agent.
For example: In this reaction copper (2) oxide is losing oxygen (O2) and is being reduced to copper. Hydrogen ( H2) is gaining oxygen & is being oxidized.
As here one reactant gets oxidized while the other gets reduced during a reaction, therefore it is an example of an oxidation-reduction reaction or redox reaction.
Another Example of redox reactions is Zinc oxide reacts with carbon to form Zn and carbon monoxide. Here Zn oxide has been reduced to Zn and carbon has been oxidized to carbon monoxide.