6. Types of Chemical Reactions

We have learned in previous class that atoms of one element do not change into those of another element during a chemical reaction., Nor do atoms disappear from the mixture or appear from elsewhere. Chemical reactions give rise to new substances that form and break bonds between atoms. You will study about types of bonds formed between atoms in (carbon and its compounds and periodic classification of elements)

 

Chemical reactions can be divided into different classes. This classification is based on the specific properties and the nature of the reactions. The chemical reactions have been divided into the following types. These are

  

Activity \(1.4\): The goal of the experiment is to see how the combination reaction will take place.

 

  

-Calcium oxide

-Beaker and

-Water

 

 

Step 1: Take some calcium oxide.

Step 2: Slowly add water to this calcium oxide.

Step 3: Slacked lime is formed, releasing a large amount of heat.

 

  

The beaker will become hot from the outside because of the liberation of a large amount of heat.

 

  

Calcium oxide combines vigorously with water to produce calcium hydroxide (slacked lime), releasing a large amount of heat.

 

  

  

In this activity, calcium oxide and water combine to form calcium hydroxide, a single product. This reaction (two or more reactants combined to form a single product) is a combination reaction.

 

\(CaO\) + \(H_2O\) → \(Ca(OH)_2\) (calcium hydroxide)

lime                                 lime water (colourless)

 

A solution of slaked lime formed by the above reaction is used for whitewashing walls.

Calcium hydroxide reacts gently with the carbon dioxide in the air to produce a thin layer of calcium carbonate on the walls.