Chemical Reactions and Equations.

1. Types of chemical reactions.

1.1. Combination Reactions.

1.1.1. Those reactions in which two or more elements or compounds combine together to form a new compound are called "combination reaction"

1.1.1.1. For Example: 2Mg(s) + O2(g) → 2MgO(s)

1.2. Redox Reactions.

1.2.1. Oxidation is defined as a process which involves loss of Hydrogen or gain of oxygen and reduction is defined as a process which involves gain of Hydrogen or loss of oxygen.

1.2.1.1. For Example: 2Mg(s) + 02(G) → 2MgO(s)

1.3. Decomposition Reactions.

1.3.1. Those reactions in which a single compound breaks downs to give two or more simpler substances are called "Decomposition Reactions"

1.3.1.1. For Example: 2Pb(NO3)2(s) → 2PbO(s) +4NO2(g) + 02(g)

1.4. Double Displacement Reactions.

1.4.1. Those reactions in which two ionic compounds in the solution react by exchange of their ions to form new compunds are called "Double Displacement Reactions".

1.4.1.1. For Example: Bacl2(aq) + Na2SO4(aq) → BaSO4(s) + 2Nacl(aq)

1.5. Displacement Reactions.

1.5.1. Those reactions in which a more active element displaces a less active element form tits compound are called "Dispalcement reaction".

1.5.1.1. For Exmaple: Fe(s) +CuS04(aq) → FeSO4(aq) + Cu(s)

1.6. Precipitation Reactions.

1.6.1. Precipitation reaction is a reaction in which an insoluble solid called precipitate is formed that separates from the solution.

1.6.1.1. For Example: AgNO3(aq) + KCl(aq) → AgCl(precipitate) + KNO3(aq)

1.7. Neutralization Reaction.

1.7.1. A reaction in which an acid reacts with a base to form salt and water is called "Neutralization Reaction".

1.7.1.1. For Example: NaOH + HCl → NaCl + H2O

2. Chemical Reactions.

2.1. Characteristics

2.1.1. 1) change in state 2) change in color 3) evolution of a gas 4) change in temperature. 5) Formation of precipitate.

2.1.2. 1) Follow the law of conservation of mass 2)Same number of atoms on both sides of the reaction

2.2. Represented by

2.2.1. Chemical Equation

2.2.1.1. Balanced Chemical Equation

2.2.1.2. Unbalanced Chemical Equation

2.2.2. Reactants --> Products

3. Heat Exchange

3.1. Exothermic Reactions

3.1.1. Chemical reactions that absorb (or use) energy overall are called endothermic.

3.1.1.1. For example: C(s) + O2(g) → CO2(g) + heat.

3.2. Endothermic Reactions

3.2.1. The chemical reaction in which heat is given out is called exothermic reactions.

3.2.1.1. For Example: photosynthesis, evaporating liquids, melting ice, dry ice.

4. Corrosion: Corrosion is the process of slowly eating up metals by gas and water vapours present in the atmosphere due to the formation of certain compounds like oxide, sulphides, carbonate, etc.

5. Rancidity: The oxidation of oils and fats in a food resulting into bad taste or odor is called "Rancidity".

6. Thermal Decomposition Reaction (In the presence of heat).

7. Electrolytic Decomposition Reaction (Electrolysis). (In the presence of electric current).

8. Photo Decomposition Reactions. (In the presence of light).