Chemical reactions and equations (2).pptx

Chemical reaction and equation by Vinay Ganesh kadam.

1. Chemical reactions and equations Presentation by – Sangita Nikalje KV No. 1 Dehuroad , Pune

2. The change that is irreversible and we get new substance is called as chemical change Chemical change

3. 1. Change in state 2. Change in colour 3. Evolution of gas 4. Change in temperature Observations in a chemical reaction

4. It is a equation showing a chemical reaction Symbols of elements are used It has two sides separated by an arrow Left side of the arrow has reactants and right side of the arrow has products If something is written on the arrow, these are the conditions required for the reactions to happen E.g. 2Mg + O 2 2MgO Chemical equation

5. Steps of balancing chemical equations Count the number of atoms of each element on LHS and RHS Start balancing the equation with elements having maximum number of atoms Generally balance oxygen/hydrogen atoms at the end Check whether all the elements are balanced Write the physical state of the elements Balancing chemical equations

6. NaOH + H 2 SO 4 Na 2 SO 4 + H 2 O Elements LHS RHS Na 1 2 O 5 5 H 3 2 S 1 1 Sodium and hydrogen are atoms are imbalanced Start balancing sodium – to balance sodium write coefficient of sodium as 2 on LHS 2NaOH + H 2 SO 4 Na 2 SO 4 + H 2 O In the process oxygen got imbalance To balance oxygen and hydrogen multiply water molecule with 2 on RHS 2NaOH + H 2 SO 4 Na 2 SO 4 + 2H 2 O The reaction is balanced

7. 1. Combination reaction 2. Decomposition reaction 3. Displacement reaction 4. Double displacement reaction 5. Oxidation reaction 6 Reduction reaction 7. Redox reaction Types of chemical reactions

8. A reaction in which two or more reactants react to give single product is called as combination reaction E.g. C + O 2 CO 2 Combination reaction

9. A reaction in which one reactant breaks down to give two or more products is called as decomposition reaction Types of decomposition reaction A. Thermal decomposition – Breaking a compound using heat energy E.g. CaCO 3 CaO + CO 2 B. Electrolytic decomposition – Breaking a compound using electric energy E.g. H 2 O H 2 + O 2 C. Photolytic decomposition – Breaking a compound using light energy/sunlight E.g. 2AgCl 2Ag + Cl 2 Decomposition reaction

10. Reaction in which more reactive metal displaces less reactive metal from its salt solution is called as displacement reaction E.g. CuSO 4 + Fe FeSO 4 + Cu Displacement reaction

11. The reaction in which there is exchange of ions is called as displacement reaction E.g. Na 2 SO 4 + BaCl 2 BaSO 4 + 2NaCl Double displacement reaction

12. The reaction in which oxygen is gained is called as oxidation reaction E.g. 2Cu + O 2 2Cuo Oxidation reaction

13. The reaction in which oxygen is lost is called as reduction reaction E.g. CuO + H 2 Cu + H 2 O Reduction reaction

14. The reaction in which oxidation and reduction happen simultaneously is called redox reaction E.g. E.g. CuO + H 2 Cu + H 2 O Redox reaction

15. Oxidizing agent is the substance losing oxygen or gaining hydrogen Reducing agent is the substance gaining oxygen or losing hydrogen CuO + H 2 Cu + H 2 O In the above reaction copper is losing oxygen so it is oxidizing agent whereas hydrogen is gaining oxygen so it is a reducing agent Oxidizing agent and Reducing agent

16. Exothermic reaction – A reaction in which heat is evolved is called an exothermic reaction E.g. CH 4 + O 2 CO 2 + H 2 O Endothermic reaction – A reaction in which heat is absorbed is called as an endothermic reaction E.g. CaCO 3 CaO + CO 2 Precipitation reaction – A reaction in which precipitate ( solid form ) is formed called as precipitation reaction E.g. Na 2 SO 4 + BaCl 2 BaSO 4 + 2NaCl Some other types of reactions

17. Attack on metal surface by air, moisture, acid etc damaging the metal is called as the corrosion Corrosion of iron is called as rusting . Iron reacts with moisture and air and form iron oxide . It is brown in colour and makes iron articles weak Corrosion of silver is called as tarnishing . Silver reacts with hydrogen sulphide gas present in the air forming silver sulphide which is black in colour Copper reacts with the carbon dioxide of the air forming copper carbonate which is green in colour Corrosion

18. 1. Keeping metals away from air and moisture 2. Painting 3. Galvanisation 4. Greasing 5. Oiling 6. Alloying etc Prevention of corrosion

19. The process of oxidation of fats and oils present in the food is called as rancidity. When the food becomes rancid its odour , colour and taste are changed Prevention from Rancidity 1. Keeping the food in air tight containers 2. Nitrogen flush 3. Adding antioxidants Rancidity