3. Effects of Oxidation Reactions in Everyday Life

Effects of Oxidation Reactions in Everyday life: Corrosion and Rancidity.

Corrosion: The process of slow conversion of metals into their undesirable compounds due to their reaction with oxygen, water, acids, gases etc. present in the atmosphere is called Corrosion.

Example: Rusting of iron.

Corrosion of Copper: Copper objects lose their lustre and shine after some time because the surface of these objects acquires a green coating of basic copper carbonate, CuCO3.Cu(OH)2 when exposed to air.

Corrosion of Silver Metal: The surface of silver metal gets tarnished (becomes dull) on exposure to air, due to the formation of a coating of black silver sulphide(Ag2S) on its surface by the action of H2S gas present in the air.

Rancidity: The taste and odour of food materials containing fat and oil changes when they are left exposed to air for a long time. This is called Rancidity. It is caused due to the oxidation of fat and oil present in food materials.

Methods to prevent rancidity:

By adding anti-oxidant.

Vacuum packing.

Replacing air by nitrogen.

Refrigeration of foodstuff.

A. Chemical Reaction: During the chemical reactions, the chemical composition of substances changes or make new substances are formed known as chemical reaction.

B. Chemical Equation: Chemical reactions can be written in chemical equation form which should always be balanced are know as chemical equation.

C. Types of Chemical Reactions:

Combination reaction: A single product is formed from two or more than two reactants.

2Mg + O2 → 2MgO

Decomposition reaction: A single reactant breaks down two or more then two 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.this format call di

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

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.

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