Types of Chemical Reactions

1. Types of Chemical Reactions The five types of chemical reactions in this unit are: Combustion Synthesis Decomposition Single Displacement Double Displacement You need to be able to identify the type of reaction and predict the product(s)

2. Combustion Reaction When a substance combines with oxygen, a combustion reaction results For example: S + O2 SO2 + energy A combustion reaction may also be the burning of a fuel

3. Combustion Methane, CH4, is natural gas and we burn it to heat our homes When hydrocarbon compounds are burned in oxygen, the products are water and carbon dioxide CH4 + O2 CO2 + H2O Balanced equation: CH4 + 2O2  CO2 + 2H2O

4. Combustion Reactions Combustion reactions involve light and heat energy released Natural gas, propane, gasoline, etc. are burned to produce heat energy Most of these organic reactions produce water and carbon dioxide

5. Steps to Writing Reactions Some steps for writing reactions: Identify the type of reaction Predict the product(s) using the type of reaction as a model Balance it Don’t forget about the diatomic elements! (HOBrFINCl twins) For example, Oxygen is O2 as anelement In a compound, it can’t be a diatomic element because it’s not an element anymore, it’s a compound!

6. Classifying Chemical Reactions combustion: AB + oxygen oxides of A & B synthesis: A + B  C decomposition: AB  A + B single displacement: A + BC  AC + B double displacement: AB + CD  AD + CB

7. Synthesis Reactions • Two or more elements combine to form a more complex compound • A + B  AB • Hand + kerchief  handkerchief • Example: C + Cl2 CCl4

8.  C C C C C C C C C C C C C C C C + O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O Synthesis Reaction Example C + O2  CO2 General: A + B  AB

9. Decomposition Reactions • Breaks down compounds into simpler substances • AB  A + B • Schoolbook  school + book • Example: Al2O3  Al + O2

10.  Na Na Cl Cl Decomposition Reaction Example: NaCl Cl2+Na Cl + General: AB  A + B

11. Hg Hg Hg Hg  + O O O O Decomposition Reaction Example 2HgO  2 Hg + O2 General: AB  A + B

12. Displacement Reactions • A reaction in which one element replaces another in a compound, or two elements in different compounds trade places • AB + C  AC + B (Single Displacement) • AB + CD  AC + BD (Double Displacement)

13. + +  Cl Cl Cl Cl Zn Zn Cu Cu Single displacement Example: Zn + CuCl2 ZnCl2 + Cu General: AB + C  AC + B

14. Ca Ca  + + Mg Mg S S O O Double displacement Example: MgO + CaS MgS + CaO General: AB + CD  AD + CB

15. Checklist for Figuring out Type of Chemical Reaction Taking Place • Follow this series of questions. When you can answer "yes" to a question, then stop! • 1) Does your reaction have oxygenas one of it's reactants andcarbon dioxide andwater asproducts?If yes, then it's a combustion reaction

16. 2)Does your reaction have two (or more) chemicals combining to form one chemical?If yes, then it's a synthesis reaction 3)Does your reaction have one large molecule falling apart to make several small ones?If yes, then it's a decomposition reaction

17. 4)Does your reaction have any molecules that contain only one element?If yes, then it's a single displacement reaction 5)If you haven't answered "yes" to any of the questions above, then you've got a double displacement reaction