CHEMICAL REACTIONS AND EQUATIONS

OXIDATION

ADDITION OF OXYGEN

C+O2----->CO2

REMOVAL OF HYDROGEN

LOSS OF ELECTRONS[LEO]

PRACTICAL APPLICATIONS-
Corrosion,
Bleaching,
Antiseptics,
Combustion,etc.

REDUCTION

REMOVAL OF OXYGEN

CuO +H2----->Cu +H20

ADDITION OF HYDROGEN

GAIN OF ELECTRONS[GER]

PRACTICAL APPLICATIONS-
Photography,
Antioxidants,
Photosynthesis,
Metallurgy,etc.

EXAMPLES

CuO+Mg------>Cu+MgO
Copper-reduced-lost oxygen
Mg-oxidised-got oxgen

Fe2O3+3CO----->2Fe+3CO2
Iron-reduced-lost oxygen
Carbon-oxidised-got oxygen

IMPORTANT POINTS TO REMEMBER-
1]Oxidation and reduction always act in pairs in a chemical reaction
2]Oxidation and reduction exactly contradict each other

CHANGE IN STATE-
BURNING OF COAL
C+O2--->CO2
Carbon-solid[coal]
Oxygen-gas
Carbon dioxide-gas

EVOLUTION OF GAS-
METAL AND ACID
Zn+H2SO4---->ZnSO4+H2
Hydrogen gas is liberated

FORMATION OF A PRECIPITATE-
Precipitate is always insoluble
Ca(OH)2+CO2--->CaCO3+H3O
CaCO3-Calcium carbonate is precipitated

CHANGE IN COLOUR-
Rusting of iron
Fe +O2+H2O--->Fe2O3.xH2O
Iron is grey in colour whereas rust is brown

CHANGE IN TEMPERATURE
CaO+H2O---->Ca(OH)2
VESSEL BECOMES HOT

CORROSION

WHEN A METAL IS ATTACKED BY SUBSTANCES AROUND IT SUCH AS MOISTURE , ACIDS ,etc.IT IS SAID TO CORRODE AND THE PROCESS IS KNOWN AS CORROSION

METHODS FOR PREVENTING CORROSION

OIL PAINTING-It prevents the atmospheric moisture from interacting with the metal

ALLOYING-Other matals are added in a fixed composition

ELECTROPLATING,GALVANISATION-Alayer of non reactive metal is plated on the object which cuth the contact with gases

APPLYING OF OIL/GREASE

RANCIDITY

WHEN FATS AND OILS ARE OXIDISEDTHEY BECOME RANCID AND THEIR TASTE AND SMELL CHANGE.

METHODS FOR PREVENTING RANCIDITY

REFRIGERATION

ADDING ANTIOXIDANTS

VACUUM PACKAGING

USING INERT GASES LIKE NITROGEN TO FILL THE PACKS

Mg(s)+O2(g)-------->MgO(s)

Burning of magnesium ribbon

Mg burns with a dazzling flame and changes into a white powder i.e. magnesium oxide.

Pb(NO3)2+KI--------->PbI2+KNO3

Takes place in aqeous medium,it is a double displacement precipitation reaction, PbI2 occurs as a yellow precipitate

Zn+HCl------->ZnCl2+H2

Acid should be dilute(aqueous).Type of exothermic, displacement reaction.

Fe+H2O--------->Fe2O3+H2

Rusting of iron

CO+H2------>CH3OH

Reaction takes place only under a pressure of 340atm

CO2+H2O------->C6H12O6+O2+H20

Known as the reaction of photosynthsis

Occurs only in the presense of sunlight and chlorophyll

Type of endothermic reaction as energy in the form of sunlight is absorbed

CaO+H2O---->Ca(OH)2

Combination and exothermic reaction

Used in white washing of walls

Ca(OH)2 on reacting with atmospheric CO2 forms a layer of CaCO3 ,Intrestingly the chemical formula of marble is also CaCO3

CH4(g)+O2(g)------>CO2(g)+H2O(g)+Energy

Exothermic reaction

Burning of methane

FeSO4(s)----->Fe2O3(s)+SO2(g)+SO3(g)

Ferric Oxide is a solid while SO2 and SO3 are gases

CaCO3----->CaO+CO2

Endothermic,Decomposition reaction

Pb(NO3)2----->PbO+NO2+O2

Thermal Decomposition reaction

AgCl------>Ag+Cl2

Photolytic decomposition reaction

Fe+CuSO4------->FeSO4+Cu

Double Displacement reaction

Zn+CuSO4------>ZnSO4+Cu

Double Displacement reaction

Pb+CuCl2------>PbCl2+Cu

Double Displacement reaction

Na2SO4+BaCl2--------->BaSO4+NaCl

Double Displacement reaction

Cu+O2------->CuO

Combination reaction

Oxidation

Copper gained Oxygen

CuO+H2-------->Cu+H2O

REDOX Reaction

Copper lost oxygen
REDUCTION

Hydrogen gained oxygen
OXIDATION

THE REACTIONS IN WHICH THERE IS AN EXCHANGE OF IONS BETWEEN THE REACTANTS ARE CALLED DOUBLE DISPLACEMENT REACTIONS

Na2SO4+BaCl2---->BaSO4+NaCl

WHEN ONE ELEMENT IS DISPLACED BY THE OTHER IN A CHEMICAL REACTION,THE REACTION IS KNOWN AS A DISPLACEMENT REACTION

Fe+CuSO4----->FeSO4+Cu

Zn+ CuSO4------>ZnSO4+Cu

A MORE REACTIVE ELEMENT CAN DISPLACE A LESS REACTIVE ELEMENT,WHEREAS A LESS REACTIVE ELEMENT CANNOT DISPLACE A MORE REACTIVE ELEMENT

WHEN TWO OR MORE SUBSTANCES COMBINE TO FORM A SINGLE PRODUCT,THE REACTIONS ARE CALLED AS COMBINATION REACTIONS

2H2+2O2------>2H2O

WHEN A SINGLE SUBSTANCE BREAKS TO FORM 2 OR MORE COMPOUNDS ,THE REACTION IS KNOWN AS DECOMPOSITION REACTION.

THERMAL DECOMPOSITION

HEAT ENERGY IS NEEDED

CaCO3---->CaO+H2O

PHOTOLYTIC DECOMPOSITION

LIGHT ENERGY

AgBr(s)---->Ag(g)+Br(g)
AgCl(s)----->Ag(g)+Cl(g)
these reactions are used in black white photography

ELECTROLYTIC DECOMPOSITION

ELECTRIC ENERGY

H2O(l)------->H2(g)+O2(g)

ELECTROLYSIS OF WATER

OXYGEN IS FORMED AT ANODE
HYDROGEN IS FORMED AT CATHODE

VOLUME OF BOTH THE GASES IS EQUAL

AN ACID/BASE/SALT IN SMALL QUANTITY HAS TO BE ADDED FOR THE CONDUCTION OF ELECTRIC CURRENT BY PROVIDING FREE IONS

EXOTHERMIC REACTION

HEAT IS RELEASED ALONG WITH THE FORMATION OF PRODUCTS

Respiration,Digestion and Composting are some of the real life examples of EXOTHERMIC REACTIONS.

ENDOTHERMIC REACTIONS

HEAT IS NEEDED FOR THE FORMATION OF PRODUCTS

AgNO3----->Ag+NO3

Ba(OH)2+NH4Cl-------->BaCl2+NH3+H2O

Vessel becomes cold i.e. heat energy is absorbed from the surroundings

LAW OF CONSERVATION OF MASS-
MASS IS NOR CREATED NOR DESTROYED IN A CHEMICAL REACTION

UNBALANCED CHEMICAL EQUATION IS CALLED A SKELELAL EQUATION

SKELETAL EQUATION-==>Fe+H2O--------->Fe2O3+H2

TOTAL MASS OF THE ELEMENTS PRESENT IN THE PRODUCTS OF A CHEMICAL REACTION,HAS TO BE EQUAL TO THE MASS OF THE ELEMENTSPRESENT IN THE REACTANTS
IN OTHER WORDS,THE NUMBER OF ATOMS REMAINS THE SAME,BEFORE AND AFTER A CHEMICALREACTION,HENCE WE HAVE TO BALANCE A CHEMICAL REACTION.

TO MAKE A CHEMICAL EQUATION MORE INFORMATIVE,THE PHYSICAL STATES OF THE REACTANTS AND PRODUCTS ARE MENTIONED ALONG WITH THEIR CHEMICAL FORMULAE