Types of Chemical Reactions

1. Types of Chemical Reactions

2. First a few concepts to take into consideration… In Unit 4 we learned how bonds are formed from elements, called compounds. In Unit 5 we will learn how those compounds form together through a process called a chemical reaction

3. What is a Chemical Reaction? • a process in which one or more substances change to make one or more new substances. • Baking bread, a space shuttle launch, & eating lunch are all examples of this

5. What Are Some Signs of Chemical Reactions? Cu(s) + 4HNO3(aq)  Cu(NO3)2(aq) + 2NO2(g) + 2H2O

6. What Are Some Signs of Chemical Reactions? 2 AgNO3(aq) + K2CrO4(aq) Ag2CrO4(s) + 2 KNO3(aq)

7. What Are Some Signs of Chemical Reactions?

8. What Are Some Signs of Chemical Reactions?

9. How do you know a “Chemical” Reaction has taken place? • The MOST important sign • The formation of a new substance with different properties • Sugar reacting with sulfuric acid • The product is neither sugar nor acid

10. Issues To Consider • Formulas show chemistry at a standstill • Equations show chemistry in action • Every chemical compound has a formula which cannot be altered • A reaction must account for EVERY atom used • The Law of Conservation of Matter

11. Types of Chemical Reactions you NEED to know!-4 Types-

12. Reaction #1 - Synthesis • Two or more elements combine to form a single, more complex compound • The Basic Form: A + BAB • The following are examples of synthesis reactions

13. Synthesis Reactions • 2Mg + O2 → 2MgO • C + O2 → CO2 • 2Na + Cl2 → 2NaCl • MgO + H2O → Mg(OH)2

14. Reaction #2 - Decomposition • A single compound breaks down into its component parts • The Basic Form: ABA + B • The following are examples of decomposition reactions

15. Decomposition Reactions • CaCO3 → CaO + CO2 • 2KClO3 → 2KCl + 3O2 • H2SO4 → H2O + SO3 • 2NaCl → 2Na + Cl2

16. Reaction #3 - Single Replacement/Displacement • A more active element takes the place of another element in a compound & sets the less active one free. • The Basic Form: A + BC AC + B • The following are examples of single replacement/displacement reactions

17. Single Replacement/displacement Reactions • Fe + CuSO4 → FeSO4 + Cu • 2Mg + 2H2O → 2MgO+ 2H2 • 2Na + 2H2O → 2NaOH+ H2 • Cl2 + 2NaBr → 2NaCl+ Br2

18. Reaction #4 - Double Replacement/Displacement • Also called an Ionic Reaction • A reaction will occur when a pair of ions come together and change places. • Sometimes called an Ionic Reaction • The Basic Form: AB + CD AD + CB • The following are examples of single replacement/displacement reactions

19. Double Replacement/displacement Reactions • BaCl2 + Na2SO4 → 2NaCl+ BaSO4 • 2HCl + FeS → FeCl2 + H2S • NaCl + AgNO3 → NaNO3 + AgCl • HCl + NaOH → NaCl+ H2O

20. Sec. 4: Energy and Rates of Chemical Reactions • Chemical Reactions have energy going in one of two directions • Going outward – Exothermic • Using energy • Releasing energy • The amount of energy when finished is less than when you started.

21. Exothermic Reactions

22. More Exothermic Reactions… • Energy released in an exothermic reaction is often written as a product in the balanced chemical equation. • 2Na + Cl2 2NaCl + energy • This reaction continues to emphasize the Law of Conservation of Matter/Mass.

23. Exothermic Reaction Diagram Draw This!

24. Energy and Rates of Chemical Reactions • Chemical Reactions have energy going in one of two directions • Going inward - Endothermic • Energy taken in • Storing energy • The amount of energy when finished is more than when you started.

25. An Endothermic Reaction Photosynthesis is a great example of storing energy!

26. More Endothermic Reactions… • Energy that is taken in during an endothermic reaction is often written as a reactant in a chemical reaction. • Photosynthesis • 6CO2 + 6H2O + energy C6H12O6 + 6O2 • This reaction continues to emphasize the Law of Conservation of Matter/Mass.

27. Endothermic Reaction Diagram Draw This!

28. What is the Law of Conservation of Energy? • Energy cannot be created or destroyed. • However it can change forms. • Energy can be transferred • Conduction, Convection, & Radiation • The total energy before a reaction will be the same as the total energy after the reaction.

29. What is the “Rate” of a Chemical Reaction? • A chemical reaction takes place when particles collide with enough force to break bonds. • The speed at which new particles form is called the “rate of a reaction”

30. What is Activation Energy? • The smallest amount of energy molecules need to react. • For example: • Matches have two chemicals on them that will ignite to create a flame (exothermic reaction) • However, those chemicals require energy to activate them - striking the match with friction.

31. Sources of Activation Energy? • Friction • Electricity - spark • Light • Motion • Anything that transfers energy

32. What Factors Affect the Rate of Reactions? • Temperature • High temperatures = increased rate of reaction • Concentration • High concentration = increased rate of reaction • Surface Area • Greater surface area = increased rate of reaction • Inhibitors • A substance that slows down the rate of reaction • Catalysts • A substance that speeds up the rate of reaction

33. What is an Inhibitor? • A substance that decreases the rate of a reaction • Examples include: • Food preservatives • Some antibiotics • Cement setting inhibitors to prevent cement from drying too quickly

34. What is a Catalyst? • A substance that increases the rate of reaction with LESS energy. • Examples include: • Catalytic converter on cars • Some glues use a catalyst to harden the glue