TERM I CHAPTER 1- CHEMICAL REACTIONS AND EQUATIONS During chemical reactions, chemical composition of substances changes or new substances are 1. formed. 2.Chemical reactions can be written in chemical equation form which should be always balanced. 3. Types of Chemical Reactions S NO Types of reactions Examples 1 Combination reaction A single product is formed from two 2Mg +O2→2MgO or more reactants. 2 Decomposition reaction A single reactant breaks down to yield two or more products. i) Thermal decomposition 2Pb(NO3)2 → 2PbO + 4NO2 +O2 ii) Electrolysis +O2 2H2O →2H2 iii) Photo chemical reaction 2AgBr →2Ag +Br2 3 Displacement reaction One element is displaced by another Zn + ZnSO4 + Cu CuSO4→ element. 4 Double displacement reaction Exchange of ions between reactants. AgNO3 +NaCl →AgCl +NaNO3 5 Redox reaction Both oxidation and reduction take CuO + H2 Cu + H2O → place simultaneously chemical reaction in which heat energy is evolved. 4. i)Exothermic reaction:A C + (g) + heat O2 →CO2 chemical reaction in which heat energy is absorbed. ii)Endothermic reaction:A ZnCO3 + + CO2 Heat →ZnO 5 .Redox reaction:Chemical reaction in which both oxidation and reduction take place simultaneously.
TERM I CHAPTER 1- CHEMICAL REACTIONS AND EQUATIONS 1. During chemical reactions, chemical composition of substances changes or new substances are formed. 2.Chemical reactions can be written in chemical equation form which should be always balanced. 3. Types of Chemical Reactions S NO Types of reactions Examples 1 Combination reaction A single product is formed from two or more reactants. 2Mg +O2→2MgO 2 Decomposition reaction A single reactant breaks down to yield two or more products. i) Thermal decomposition 2Pb(NO3)2 → 2PbO + 4NO2 +O2 ii) Electrolysis 2H2O →2H2 +O2 iii) Photo chemical reaction 2AgBr →2Ag +Br2 3 Displacement reaction One element is displaced by another element. Zn + CuSO4→ ZnSO4 + Cu 4 Double displacement reaction Exchange of ions between reactants. AgNO3 +NaCl →AgCl +NaNO3 5 Redox reaction Both oxidation and reduction take place simultaneously CuO + H2 → Cu + H2O 4. i)Exothermic reaction:A chemical reaction in which heat energy is evolved. C + O2 →CO2 (g) + heat ii)Endothermic reaction:A chemical reaction in which heat energy is absorbed. ZnCO3 + Heat →ZnO + CO2 5 .Redox reaction:Chemical reaction in which both oxidation and reduction take place simultaneously.
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