The chemical Reaction:
* Is the process in which bonds in reactants are broken and bonds in products are formed.The chemical equation:
- It is a group of symbols and formulae written to show the reactants and products and the conditions needed for the reaction if they exist.
Types of chemical Reactions
First: Direct Combination Reaction:
- It is a reaction between two or more substances to form a new compound.
A- Element + Element:
Ignition point: - It is the minimum temperature at which the substance begins to burn.
C- Compound + Compound:
Decomposition Reaction
- The reactions in molecules of some compounds decompose into elements or simpler compounds when they are taken a certain amount of energy.
A- Thermal decomposition Reaction:
1- Some heavy oxides
2-Metal Hydroxides
3- Metal carbonates:
4-Most Sulphates:
5-Metal Nitrates
B- Electrolysis
- It is the process in which the compound decomposes into its elements by passing electric current through its molten or solution.
An electrolyte:
- Is a compound (solution or a molten) that conduct electric current and ionizes into positive and negative ions.
* Electrolysis of water:
* Hoffman's voltameter: - It is an apparatus used in electrolysis
* Its structure:
1- A glass container
2- Two electrodes "cathode and anode".
3- The electrolyte.
Activity (11):
* Electrolysis of acidified water:
- On passing electric current in water acidified by diluted sulphuric acid it decomposes into:
- Applications (uses) on electrolysis:
- Electrolysis reactions are used in several cases such as:
1- Getting oxygen and hydrogen from water.
2- Getting sodium and chlorine from molten sodium chloride.
3- Preparation of aluminum in industry.
4- In electroplating of metals such as covering a copper spoon with a layer of gold or silver.
Third: Simple Substitution Reaction:
- It is the reaction in which an element substitutes another element in a solution of one of its compounds.
Chemical activity series:
- It is the arrangement of elements in a descending order according to their chemical activity.
Types of simple substitution:
A-Substitution of hydrogen in an acid by a metal:
B- substitution of a metal by another one in its salt solution:
Fourth: Double substitution Reactions
* They are reactions in which the radicals (ions) of two compounds substitute each other giving two new compounds, without transfers of electrons.
B- Reaction between acid and salt:
C-Double substitution between two salt solutions
1- The reaction between sodium chloride solution and silver nitrate solution:
2- The reaction between barium nitrate solution and copper sulphate solution:
3- The reaction between sodium sulphide solution and copper sulphate solution
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