Chemical reaction and equation 0 notes
Answers
Class 10th
Chemistry
Chapter 1
Chemical Reaction and Equation
1. Chemical Reaction: During chemical reactions, the chemical composition of substances changes or new substances are formed.
2. Chemical Equation: Chemical reactions can be written in chemical equation form which should always be balanced.
3. Types of Chemical Reactions:
Combination reaction: A single product is formed from two or more reactants.
2Mg + O2 → 2MgO
Decomposition reaction: A single reactant breaks down to yield two or more products.
Thermal decomposition: 2Pb(NO2)2 → 2PbO + 4NO2 + O2
Electrolysis: 2H20 → 2H2 + O2
Photochemical reaction: 2AgBr → 2Ag + Br2
Displacement reaction: One element is displaced by another element.
Zn + CuSO4 → ZnSO4 + Cu
Double displacement reaction: Exchange of ions between reactants.
AgNO3 + NaCl → AgCl + NaNO3
Redox reaction: Both oxidation and reduction take place simultaneously.
CuO + H2 → Cu + H2O
Exothermic reaction: A chemical reaction in which heat energy is evolved.
C + O2 → CO2 (g) + heat
Endothermic reaction: A chemical reaction in which heat energy is absorbed.
ZnCO3 + Heat → ZnO + CO2
Redox reaction: Chemical reaction in which both oxidation and reduction take place simultaneously.
4. Oxidation: Reaction that involves the gain of oxygen or loss of hydrogen.
5. Reduction: Reaction that shows the loss of oxygen or gain of hydrogen.
ZnO + C → Zn + CO
ZnO is reduced to Zn—reduction. C is oxidized to CO—Oxidation.
6. Effects of Oxidation Reactions in Our Daily Life:
Corrosion: It is an undesirable change that occurs in metals when they are attacked by moisture, air, acids and bases.
Example, Corrosion (rusting) of Iron: Fe2O3. nH2O (Hydrated iron oxide)
Rancidity: Undesirable change that takes place in oil containing food items due to the oxidation of fatty acids.
Preventive methods of rancidity: Adding antioxidants to the food materials, storing food in the airtight container, flushing out air with nitrogen gas and refrigeration.