Chemical reactions

1
Chapter 8

• Chemical reactions

2
Chemical Reaction

• Represents a chemical change
• Reactants products
• When a chemical change occurs the products have a
  different set of properties than the reactants.
• Follows the Law of the Conservation of Mass

3
Law of the conservation of mass

• Matter can not be destroyed or created it can
  only be rearranged.
• Mass of the reactants must equal the mass of the
  products.
• That is why all chemical reactions must be
  balanced.

4
Balancing Equations

• Preliminaries- if a word problem, identify the
  reactants and the products of the reaction.
• Write the equation in chemical reaction form
• Generally stated as
• A B C
• First do an atom count of the reactants and of
  the products.
• Second adjust coefficients to make the number
  of atoms for each element equal on both sides.

5
ExampleLiAlH4 H2 O LiOH Al(OH)3
H2

• 1- Li
• 1-Al
• 6 - H
• 1- O

• 1 Li
• 1- Al
• 6- H
• 4- O

6
Example

• Al(NO3)3 NaOH Al(OH)3 NaNO3

7
Types of Chemical Equations

• Single displacement reactions
• Double displacement reactions
• Decomposition reactions
• Synthesis reactions
• Combustion reactions

8
Single and double displacement

• General form of a single displacement reaction
  
• Single Displacement
• A BC B AC
• (redox reactions)
• Double displacement
• AB CD AD CB

9
Decomposition and Synthesis

• Decomposition reactions general formula
• AB A B
• Synthesis reactions general formula
• A B AB

10
Combustion reactions

• Will always follow the same pattern- template
• A O2 CO2 H2O Energy
• C4H8 O2 CO2 H2O Energy
• C4H8 6O2 4CO2 4H2OEnergy

11
Percent Yield

• Percent yield actual amount of the product/ the
  theoretical amount of the product X 100.
• Until we do stoichiometry,the theoretical amount
  will be given to you. Once we completed 9.2, you
  will be able to find out the theoretical amount
  yourself.

12
Example

• The actual amount in a reaction is 39.7 g, the
  predicted amount was 65.6 grams. What is the
  percent yield?
• (39.7g/ 65.6g ) x 100
• 60.5

13
More on combustion equations

• Balance the equations
• Use the molar heat of combustion to find the
  amount of heat evolved.
• Review terms exothermic
• endothermic

14
Chemical reaction symbols

• Solid cr
• Gas g
• Liquid/ dissolved in water - aq