Chemistry Podcast

Monday, 27 July 2015

10 Class- Chemical Reactions and Equations

Chemical Reactions and Equations

  • ·       Every chemical change is a chemical reaction.
  • ·       General observation to identify whether a chemical reaction take place or not-
1.    Change in state.
2.    Change in color.
3.    Evolution of gas.
4.    Change in temperature.

Chemical Equations:

Any equation which describes the change of reactants to products is called chemical reaction.
Reactant1+Reactant2+…………--->   Product1+Product2+………

In chemical equations reactants are placed on left hand side and products are placed on right hand side and arrow sign is placed between them. Direction of arrow shows the direction of reaction.
Example: chemical equations in words.
Magnesium + Oxygen {Reactants} .------->  Magnesium-Oxide {Product}

Writing a Chemical Equation by using Chemical Formula:

In it we use symbols instead of words to write a chemical equation.
Example: Mg + O2 .-----> MgO

     1.    Unbalanced Chemical Equation:

Equation in which number of atoms on reactant side is not equal to number of atoms on product side, means mass is not same on both sides.
         Example: Mg + O2 -----> MgO
                          Fe +  H2-----> Fe3O4 + H2

     2.    Balanced Chemical Equation:

Equation in which number of atoms on reactant side is equal to number of atoms on product side, means mass is same on both sides.
         Example: 2Mg + O2 ----> 2MgO
                          3Fe + 4H2O -----> Fe3O4 + 4H2

Writing Symbols of Physical State:

                                                          Reactants and products are written with their physical state to make equation more informative.
Physical State
Example: 3Fe (s) + 4H2O (g) -----> Fe3O4 (s) + 4H2 (g)
·       Example of reactions with reaction condition like pressure, temperature, catalyst etc.
10 classes science chemistry note

Types of Chemical Reactions:

                                                Chemical reactions are reactions which involve making and breaking of bonds between atom to yield new substances.

    1.    Combination Reaction:

These are the reactions in which one single product is formed from two or more reactants.
Example: i. Formation of Calcium Hydroxide.
CaO (s)(quick lime) + H2O (l) -------> Ca(OH)2 (aq)(slaked lime)
ii. Burning of Coal.
C (s) + O2 (g) ------> CO2 (g)
iii. Formation of Water.
2H2 (g) + O2 (g) ------> 2H2O (l)

    2.    Displacement Reaction:

These are the reactions in which highly reactive metal displaces less reactive metal from their solution.
Example: i. Fe (s) + CuSO4 (aq)(copper sulphate) -------> FeSO4 (aq)(iron sulphate) + Cu (s)
 ii. Zn (s) + CuSO4 (aq)(copper sulphate) -------> ZnSO4 (aq)(zinc sulphate) + Cu (s)
iii. Pb (s) + CuCl2 (aq)(copper chloride) -------> PbCl2 (aq)(lead chloride) + Cu (s)

    3.    Double Displacement Reaction:

These are the reactions in which exchange of ions between reactants occur.
Example: Na­2SO4 (aq)(sodium sulphate) + BaCl2 (aq)(barium chloride) -------> BaSO4 (s)(barium sulphate) + 2NaCl (aq)(sodium chloride)

    4.    Oxidation and Reduction Reaction:

1.1.        Oxidation:

These are the reactions in which a substance loses hydrogen or gain oxygen.
          Example: 2Cu + O2 + Heat ----------> 2CuO

1.2.        Reduction:

These are the reactions in which a substance gain hydrogen or loses oxygen.
          Example: CuO + H2 + Heat ----------> Cu + H2O

1.3.        Redox Reaction:

These are the reactions in which one reactant gets reduced while other reactant gets oxidized. This type of reaction is also known as Oxidation-Reduction Reaction or Redox Reaction.
i.                   CuO + H2 + Heat ---------> Cu + H2O
In above reaction-
                   H2 ---------> H2O (oxidation)

                   CuO --------> Cu (reduction)

ii.                ZnO + C --------->  Zn + CO
iii.             MnO2 + 4HCl --------> MnCl2 + 2H2O + Cl2

Observable Effect of Oxidation Reduction in Everyday Life:

1.    Corrosion:

   Attack on metals by moisture, acids, oxygen etc., which corrode metals is called corrosion.

Example: Rusting of Iron, Black coating on Silver, Green coating on Copper.

2.    Rancidity:

   Change in taste and smell of food material prepared by using fat or oil, because fat or oil get oxidized and become rancid.

Endothermic Reaction:

                                      These are the reactions in which heat is absorbed during reaction.

Example: NH4Cl (s) + H2O (l) + Heat --------> NH4Cl (aq)

Exothermic Reaction:

                                      These are the reactions in which heat is evolved during reaction.

Example: CH4 (g) + 2O2 (g) --------> CO2 (g) + 2H2O (g) + Heat

Precipitation Reaction:

                                      These are the reactions in which insoluble substance called precipitate is obtained when reaction completes, is known as precipitation reaction.

Example: Na2SO4 (aq) + BaCl2 (aq) -------> BaSO4 (s) + 2NaCl (aq)

Saturday, 25 July 2015

Maths 5th Class

5th Class Mathematics

Mathematics is very necessary in understanding chemistry very well, so we now publish some basics of mathematics from class 5th maths. Hope you like our work.
Multiplication:  operation to get no. of times of given no. eg- 5x5 = 25
Vedic trick of multiplication-
HCM (Highest Common Multiple) and LCM (Lowest Common Multiple) :

HCM: 5

LCM: 5x3x2x5x7=1050

Profit = selling price - cost price
Loss = cost price - selling price
Profit% = (profit x 100)/cost price
Loss% = (loss x 100)/cost price
Amount = principle + interest
Simple Interest = principle x rate% x time
Simple Interest = (principle x rate x time)/100
AM = antemeridian
PM = postmeridian
Big Units
Small Units
Kilo = 1000 times
Deci = 1/10
Hecto = 100 times
Centi  = 1/100
Deco = 10 times
Mili = 1/1000
Perimeter of Triangle = sum of lengths of all three sides of triangle.
Perimeter of Rectangle = 2 (Length + Breadth)
Perimeter of Square = 4 x ( Length of any one side)
Area of Rectangle = Length x Breadth
Area of Square = Side x Side
Different Angles used in Mathematics:
  • Acute Angle < 90o
  • Right Angle = 90o
  • 90o < Obtuse Angle < 180o
  • Zero Angle = 0o
  • Straight Angle = 180o
Different Triangles used in Mathematics:
  • Right Triangle = Triangle containing one 90o angle
  • Equilateral Triangle = Triangle having three equal sides and three equal angles, and have each angle of 60°.
  • Isosceles Triangle = Triangle having two equal sides and two equal angles.
  • Scalene Triangle = triangle having different length of sides.
  • Acute Triangle = Triangle having all three angles less than 90o
  • Obtuse Triangle = Triangle having one angle more than 90o


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