Endothermic and Exothermic Reaction

A: -Endothermic: absorb energy from surrounding
     -Exothermic: release energy to surrounding
  
     Ex: Instant ice pack absorb energy and are Endothermic reaction
            Explosions release energy are exothermic reaction

     -Molecules are held together by chemical bonds
       -Add energy to break bonds---->Endothermic
       -Give off energy to form bonds--->Exothermic
      *Enthalpy, "H" is the heat contained in the system

B: We can chart the potential energy of the chemicals as they change from reactants to products

    -Reactants start with a certain amount of energy, energy is added to start the reaction and  then energy is released as the reaction processes

  -Energy of reactant: total potential energy of all reactants in the reactions
  -Energy of product: total potential energy of all products in the reactions
  -Energy of activated complex: potential energy of the transition state between reactant-product
  -Activation energy:  the energy that must be added to get the reaction to progress
  -Delta H: the change in potential energy during the reaction


C: The energy in Equation
     Ex: CH4+2O2--->CO2+2H2O+812KJ
            higher               lower
            energy             energy

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Types of Reactions

-6 generalized types of reaction
  -Synthesis
  -Decomposition
  -Single/Double Replacement
  -Combustion
  -Neutralization
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A: Synthesis A+B --> C
     -combines two or more reactants to form one product
     Ex: K + Cl --> KCl
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B: Decomposition C--> A+B
     -one compound breaks down to two or more reactants
     Ex: CaCO3 --> CaO+CO2
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C: Single Replacement A+BC --> AC+B(A=metal) or A+BC--> AB+C(A=non metal)
     -one element is replaced by another in a compound
     Ex: 2Al+3FeCl2--> 2Fe+AlCl3
           Cl2+2KBr-->Br2+2KCl
     *some metals are more reactive than other metal, same as non- metal
     *using the Activity Series ----an element higher up on the series replaces the ion below it on the table
     Ex: 2Li+MgCl2-->2LiCl+Mg  (yes)---Li is higher than Mg on the table
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D: Double Replacement AB+CD-->AD+BC
     -a double replacement is a reaction between two ionic compounds usually in solution
     Ex: Na2CO3(aq)+CaCl2(aq)-->CaCO3(s)+2NaCl(aq)
     *According to the Solubility  Table, if there is a Solid in the product side;
        this equation would be  reacted  
        Net Ionic Equation: Ca2+  +  Cl1-   -->CaCl2

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E: Combustion AB+O2----->AO+BO
     -A combustion reaction is a reaction reactants are chemical to be burned
      and the oxygen that it reacts with.
      Ex:C4H8+6O2--->4CO2+4H2O
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F: Neutralization HA+ BOH--->H2O+AB
     -A Neutralization reaction is a special double replacement reaction where acids react withe bases to produce water and an ionic salt as products
     Ex: 2HBr(aq)+Sr(OH)2(aq)--->SrBr2(aq)+H2O(l)

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Balancing Equation

-The aim of balancing an equation is to make the number of atoms of each side is equal

STEP:
1.balance the atoms which only occur in one molecule
2.balance whole groups whenever possible (SO4,NO3,ClO3...)
3.Balance atoms which occur in elemental form last

1PbO2+4HBr--->2H2O+1PbBr2+1Br2

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Translating Word Equation

1: Calcium carbonate solid and hydrobromic acid react to form carbon dioxide gas,      aqueous calcium bromide and liquid water
   --CaCO3(s)+HBr(aq)---->CO2(g)+CaBr2(aq)+H2O

2: Aqueous sodium hydrogen carbonate reacts with sulphuric acid to produce aqueous sodium sulphate water, and carbon dioxide gas.
   --2NaHCO3(s)+H2SO4(aq)---->Na2SO4(aq)+2H2O(l)+2CO2(g)


3: Sodium metal reacts with water to produce solid sodium hydroxide and hydrogen gas
   --2Na+2H2SO4(aq)---->2NaOH(aq)+H2(g)