1. UNIT 12: CLASSIFICATION OF CHEMICAL REACTIONS 1

2. Chemical Reactions a process that involves changes in the structure and energy content of atoms, molecules, or ions but not their nuclei. 2

3. Most reactions occur in the aqueous phase (in water) because the particles can move about and interact with each other. 3

4. Remember This? Dissolving- a solvent surrounds a solute. Watch This 4

5. Formation of Solutions -Dissolving A solute dissolving in a solvent requires energy. It can be an endothermic or exothermic process. Is it a chemical reaction? 5

6. Formation of Solutions- Dissolving Covalent molecules … DO NOT break apart when dissolved. Ionic Compounds… DO break apart when dissolved (this is considered a chemical change) 6

7. Molarity A unit of concentration The number of moles of solute dissolved in 1.00 L of solution. Molarity (M) = Moles of solute Liter of solution 7

8. Practice Problem What is the molarity if 2.0 moles of glucose are added to 5.0 L of solution? 8

9. Practice Problem Molarity (M) = Moles of solute Liter of solution 2.0 moles =.40 M 5.0 L 9

10. How to prepare a solution 10 Grams = Molarity X Liter X Molar Mass of Solute solute Watch This

11. How to prepare a solution 11 To make a concentrated solution more dilute use this formula M 1 V 1 = M 2 V 2 M 1 = concentrated solution V 1 = amount of concentrated solution need to make dilute solution M 2 = dilute solution V 2 – amount of diluted solution wanted.

12. Law of Conservation of Matter matter cannot be created or destroyed, it can only change forms. Therefore, in a chemical reaction the number of atoms, the mass and the charge must be conserved. Watch This reactants products Activated complex 12

13. EQUATIONS Balancing Equations – In order to be balanced, the type and number of atoms must match on the reactant and product side 13

14. Balancing Equations- Taking inventory Reactants 4 hydrogen 2 oxygen Products 4 hydrogen 2 oxygen In order to be balanced, the type and number of atoms must match on the reactant and product side 14

15. Tutorial and Practice Tutorial Watch This Practice 15

16. __H 2 S(g) + __SO 2 (g)  __S(s) + __H 2 O(g) Reactants Products 16

17. __Fe 2 O 3 (s) + __H 2 (g)  __Fe(s) + __H 2 O(g) ReactantsProducts 17

18. Types of Reactions Combination/Synthesis/Composition A + B  AB Decomposition AB  A + B Single Replacement C+ AB  AC + B Double Replacement AB + CD  AD + CB Combustion C x H y + O 2  CO 2 + H 2 O Redox – any of the above where the oxidation number of two species changes 18 +

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23. Double Replacement Clue: Do-See-Doh AB + CD  AD + CB 23

24. Combination 1 Also known as composition or synthesis; one product http://genchem.chem.wisc.edu/demonstrations/Gen_Chem_Pages/04chemrxnpage/chemicalreactions.htm ___K (s) +___Br 2 (l)  ___KBr (s) 24

25. Combination 2 ____Zn (s) + ___I 2 (l)  ____ ZnI 2 (s) http://genchem.chem.wisc.edu/demonstrations/Gen_Chem_Pages/04chemrxnpage/chemicalreactions.htm 25

26. Decomposition Single reactant breaks down into two or more simpler substances 26

27. Single Replacement A single element replaces another element in a compound. Must use activity series to determine if reaction will take place. More active will replace less active. ___Cu (s)+ __AgNO 3 (aq)  __Cu(NO 3 ) 2 (aq)+ ___Ag (s) Remember: Metal can only replace metal (or hydrogen) Nonmetal can only replace nonmetal SR animation 27

28. Using the activity series: Watch This Watch This. For a single replacement to occur, the solo metal must be more reactive than the metal it replaces. The higher up on the list, the more reactive it is. 28

29. Single Replacement For a single replacement to occur, the solo nonmetal must be more reactive than the nonmetal it replaces. The higher up on the list, the more reactive it is. 29

30. Double Replacement Two reacting compounds, with metals trading places. A precipitate (insoluble solid) is formed. ___AgNO 3 (aq)+ ____NaCl (s)  ____NaNO 3 (aq)+ ____AgCl (s) 30

31. Determining solubility of products Use the solubility rules on the back of the periodic table. The solubility rules are organized by the anion in the compound. Find the anion. * this is the negative ion * Determine if, based on the cation, the compound is soluble (aq) or insoluble (s) in water. Write the (aq) or (s) after the compound Practice: AgCl K(NO 3 ) PbS 31

32. Solubility Shortcuts – here’s all you need to remember: All group 1 metals All nitrates (NO 3 - ) All acetates (C 2 H 3 O 2 - ) All ammonium (NH 4 + ) ARE ALWAYS SOLUBLE (aq) Remember HAP Stands for Mercury (Hg), Silver (Ag) and Lead (Pb) Compounds with these elements are usually INSOLUBLE (s) 32

33. Try these: NaC 2 H 3 O 2 Hg(OH) 2 MgBr 2 (NH 4 ) 2 SO 4 33

34. Combustion _C 3 H 8 + _O 2  _ CO 2 + _H 2 O + energy A combustion reaction is when oxygen combines with another compound to form water and carbon dioxide. It is highly exothermic. 34

35. OXIDATION-REDUCTION REACTIONS a reaction where electrons are transferred between reactants and products Watch This 35

36. OXIDATION-REDUCTION REACTIONS a. Loss of Electrons is OXIDATION i. oxidation number increases across the arrow. b. Gain of Electrons is REDUCTION i. oxidation number decreases across the arrow. *LEO the Lion Says GER- These must occur together. Can’t have one without the other. 36

37. OXIDATION-REDUCTION REACTIONS Oxidation Number (Oxidation State) – a method of keeping track of electrons gained (reduced) and lost (oxidized). 37

38. OXIDATION-REDUCTION REACTIONS Rules for assigning oxidation numbers a. Atoms in their elemental form have an oxidation number of zero. Cu = 0 b. Monatomic ions have an oxidation number equal to their charge. K +1 = +1. c. Nonmetals have negative oxidation numbers. i. Oxygen is -2 in all compounds with the exceptions of peroxides in which it is -1 ii. Hydrogen is usually +1 with nonmetals Hydrogen is usually -1 with metals d. The sum of the oxidation number in an neutral compound is zero. 38

39. OXIDATION-REDUCTION REACTIONS How to identify a redox reaction. a. Determine the oxidation number of each element in each compound. b. Compare the reactants and products. c. If there is a change in the oxidation number of any species, then it is redox. d. Number increases across arrow = oxidation LEO e. Number decreases across arrow = reduction GER 39

40. OXIDATION-REDUCTION REACTIONS Practice- are the following redox reactions? ______ a. NaCl + AgNO 3 --> NaNO 3 +AgCl ______ b. FeCl 2 + Cl 2  FeCl 3 40