2. Chemical Reactions and Collision Theory Chemistry I 2007

3. Chemical reaction Format Generic Format A + B C + D ReactantsProducts Substances being mixed LHS of arrow Substance being made RHS of arrow “Yield” = reaction taking place

4. Types of Chemical Reactions 5 main types of Chemical Reactions 1) Synthesis 2) Decomposition 3) Single Displacement 4) Double Displacement 5) Combustion

5. Synthesis Synthesis means “to make” Generic RXN A + BC Always makes 1 product Real Life reaction Fe Iron main component in steel Oxygen Iron (III) Oxide AKA RUST Fe 2 O 3 + O 2

6. Decomposition Decomposing video Generic Reaction A B + C Only 1 Reactant Real Life Reaction H 2 O 2 H 2 + O 2 Hydrogen Peroxide

7. Single Displacement Generic Reaction A + XYX + AY OR A + XYY + XA Metal for a metal Non-metal for a Non-metal

8. Single Displacement A + XYX + AY Always a Single Element Always a Compound (2 or more elements)

9. Single Displacement Al + HClH 2 + AlCl 3 Single Element Compound (2 or more elements)

10. Double Displacement Generic Reaction AB + XY XB + AY 2 Compounds (2 or more elements bonded together)

11. Double displacement KI + Pb(NO 3 ) 2 Compound 1Compound 2 PbI 2 + KNO 3 K and Pb switch

12. Combustion Generic reaction CxHyCxHy + O 2 CO 2 + H 2 O ALWAYS Hydrocarbon Burning a substance in the presence of oxygen (O 2 )

13. Combustion C 8 H 18 + O 2 CO 2 + H 2 O Octane Gasoline CH 3 OH + O 2 CO 2 + H 2 O Methanol

14. Chemical Reaction Review Generic Format of reaction 5 different types of chemical reactions A + B C + D ReactantsProducts A + B C + D Products 1) Synthesis 2) Decomposition 3) Single Displacement 4) Double Displacement 5) Combustion

15. How do reactions occur? Collision Theory Collision Theory In order for a chemical reaction to take place, the reactants must collide. The collision transfers kinetic energy needed to break the necessary bonds so that new bonds can be formed.

16. Collision requirements Requirement 1 Must have the proper orientation. 2HCl + Mg  MgCl 2 + H 2 H---ClMg Wrong Orientation H-ClMgH Cl-Mg  Correct Orientation

17. Collision requirements Requirement 2 Mg Must have enough kinetic energy to reach a threshold of energy called activation energy H---Cl Mg H Cl--Mg

18. Energy of Activation

20. Increasing the Rate of Reactions What needs to happen in order for the rate of the chemical reaction to increase (go faster)? More collisions= Faster reaction rate

21. 4 Factors that cause more collisions 1)____________ 2)____________ 3)____________ 4)____________

22. 5 th way in increase Rxn Rate Add a Catalyst = Speeds up a reaction but is not used in the reaction  Lowers the activation energy

23. Summary Molecules must collide with the correct orientation and enough energy in order to react. More collisions Faster the reaction rate. Increase Temperature, Concentration, Pressure, and surface area results in more collisions therefore faster reactions. Adding a catalysts lowers the energy of activation thus faster reaction rate.