1. What is meant by Chemical combination?
The reaction in which two or more substances combine to give a single substance is called Chemical combination.
eg:- S + O2 → SO2
C + O2 → CO2
2. What are the different types of Chemical changes?
The different types of Chemical changes are
1. Chemical combination
2. Chemical decomposition
3. Chemical displacement
4. Chemical double decomposition
3. Give two examples for Chemical decomposition?
1. Decomposition of Calcium carbonate (CaCO3)
CaCO3 decomposes on heating to form two substances - Calcium oxide (CaO) and Carbondioxide.
CaCO3 → CaO + CO2
2. Decomposition of hydrogen peroxide
Hydrogen peroxide decomposes into water (H2O) and oxygen (O2).
2H2O2 → 2H2O + O2
4. What is meant by Chemical decomposition?
The reaction in which a single substance split into two or more substances are called Chemical decomposition.
eg:- CaCO3 → CaO + CO2
5. Give one example for Chemical displacement
When Zinc is added to copper sulphate solution, Zinc displaces copper from CuSO4 and forms colourless Zinc sulphate
Zn + CuSO4(Copper sulphate) → ZnSO4 (Zinc sulphate) + Cu
6. Define Chemical displacement
The reaction in which one element or radical replaces another element or radical in a substance is called Chemical displacement.
eg:- Zn + CuSO4 → ZnSO4 + Cu
7. Explain the type of chemical change taking place in the reaction Br2 + 2KI → 2KBr + I2↑
In the reaction Br2 + 2KI → 2KBr + I2, Bromine displaces Iodine from Potassium iodide liberating iodine gas. This is an example for chemical displacement reaction.
8. What is meant by chemical double decomposition?
The reaction in which the elements exchange their radicals to form two new compounds is called double decomposition.
eg:- BaCl2 + Na2SO4 → BaSO4 + 2NaCl
9. Give two examples for chemical double decomposition reaction
1. AgNO3 + NaCl → AgCl ↓ + NaNO3
Silver (Ag) and Sodium (Na) exchange their constituents and form two new substances.
2. BaCl2 + Na2SO4 → BaSO4 + 2NaCl ;
In this reaction barium (Ba) and Sodium (Na) exchange their anions to give two new compounds.
10. Give one example each for reversible and irreversible chemical double decomposition reaction
Chemical changes are reversible and irreversible.
AgNO3 + HCl → AgCl + HNO3
This reaction is irreversible ie, products donot combine to give reactants.
PCl5 ↔ PCl3 + Cl2
This reaction is reversible. The product can be changed to reactant depending upon experimental conditions.