2. CHEMICAL REACTIONS CHAPTER 8

3. Evidence of a Chemical Rx 1. Color change 2. Formation of a gas 3. Heat produced or heat absorbed 4. Formation of a precipitate 5. New odor 6. Production of light

4. I. CHEMICAL EQUATIONS Defined Defined 1.Are a condensed statement of facts about a chemical reaction 2Na + Cl 2  2NaCl

5. I.CHEMICAL EQUATIONS BONDING ENERGY 2.Represent the changes in BONDING and ENERGY that take place in a reaction 2Na + Cl 2  2NaCl A. Defined

6. II. Information in an Equation A.Reactants: 1.are all substances that exist the reaction 2.are always located to the 2Na + Cl 2  2NaCl before left of the arrow

7. II. Information in an Equation B.Products: 1.are all substances that exist the reaction 2.are always located to the 2Na + 1Cl 2  2NaCl after right of the arrow

8. II. Information in an Equation C.Arrows: 1.Horizontal Arrows Stand for or 2Na + 1Cl 2  2NaCl yields produces

9. II. Information in an Equation C.Arrows: 2.Vertical Arrows  indicates that the substance will leave the reaction as a gas ( ) HCl + Zn  H 2  + ZnCl 2 effervescence

10. II. Information in an Equation C.Arrows: 2.Vertical Arrows  indicates that the substance settles to the bottom of the solution as a solid AgNO 3 + Zn  Ag  + Zn(NO 3 ) 2 ( is formed) precipitate

11. II. Information in an Equation D. Showing Phase: ( ) gas ( ) liquid ( ) solid ( ) dissolved in H 2 O H 2(g) + O 2(g)  H 2 O (l) g l s aq

12. E. Coefficients: 1.are whole #’s written in front of formulas 2.indicate the ratio of each cmpd in the equation 3.are used in balanced eq.to make the # atoms of each element on the reactant side = # atoms of each element on the product side 212 2H 2(g) + 1O 2(g)  2H 2 O (l)

13. Writing Equations 1. Use chemical formulas 2.Rules – write Reactants  Products. 3.Balancing equations using Coefficient – Coefficient - is the smallest whole # that appears in front of a formula Symbols : + And  Yield (l) Liquid Gaseous product ppt Delta  Reversible rxn (g) gas (s) Solid (aq) aqueous

14. F. Showing Energy Changes: 1. Absorb energy Have + energy on reactant side 2. Release energy Have + energy on product side 1energy 2H 2(g) + 1O 2(g) + energy  2H 2 O (l) Endothermic Rxn Exothermic Rxn

15. Catalyst – is a substance that changes the rate of a chemical reaction, but can be recovered unchanged. Reversible reaction –  is a chemical reaction in which the products reform the original reactants.

16. III. Balanced Equations 1.States: A. Obey the Law of Conservation of Matter Matter cannot be created or destroyed

17. 2.Thus the number of atoms of each element on the reactant side of the equation. must the number of atoms of each element on the product side of the equation. III. Balanced Equations (not in notes) A. Obey the Law of Conservation of Matter equal

18. 3.Since the number of atoms is conserved so is the mass. If you started with 10 grams of reactants, there will be 10 grams of products. III. Balanced Equations A. Obey the Law of Conservation of Matter

19. III. Balanced Equations B.Background: 1. all atoms must be accounted for

20. 2.Use to make the total number of atoms of each element in the reactants equal the total number of atoms of each element in the products total number of atoms of each element in the products. III. Balanced Equations B.Background: coefficients

21. III. Balanced Equations B.Background: 3. Never change subscripts! 4.If an element occurs more than once on one side of the equation it is usually (but not always) best to balance it last.

22. B. Coefficients 1.Are numbers that indicate how many atoms or molecules of each substance are involved in the reaction 2.Are written in of formulas 3.Are used to balance an eq. 2 2AlCl 3 whole front

23. III. Balancing Equations C. General Rules for Balancing Eq. 1.Write the equations and balance them in 2.Count the number of atoms of each element in the reactants and products. 3. Balance the elements one at a time by using coefficients. Never change subscripts! pencil

24. III. Balancing Equations D. Steps to Balancing an Eq. 2. Balance metals 3. Balance nonmetals 4. Balance oxygen 5. Balance hydrogen 6. Recount all atoms 7. If every coefficient will reduce, rewrite in the simplest whole-number ratio.

25. III. Balancing Equations E. Sample Problems Cl 2 + NaBr  Br 2 + NaCl Al 2 (SO 4 ) 3 + CaCl 2  AlCl 3 + CaSO 4

26. III. Balancing Equations D. Steps to Balancing an Eq. 1. Check for Diatomic molecules 1. Check for Diatomic molecules if these elements never appear by themselves in an equation, they must be written with the subscript 2 H 2 N 2 O 2 F 2 Cl 2 Br 2 I 2

27. IV. Types of Reactions A. Synthesis Reaction Two or more substances combine to form a new compound. It follows this general equation: Element + Element  compd. A + X  AX Mg + O 2  +2 -2 2 MgO

28. A. Synthesis - Practice Problems 1. H + O  H 2 O Remember diatomic molecules: H, N, O, F, Cl, Br, I (Super 7) 2. S + O  SO 2 2 22 2 22 S - 1 1 O - 2 1 2222 2 IV. Types of Reactions

29. 3.Co + F  4. Na + F  5.U + F  2 +3 -1 CoF 3 +1 -1 2NaF Na -1 1 F - 2 1 2222 2 2 2 2 +6 -1 UF 6 U – 1 1 F – 2 6 3 6 A. Synthesis - Practice Problems IV. Types of Reactions

30. A single compound undergoes a reaction that produces two or more simpler substances. AX  A + X Compound  element + element 2 HgO  2 Hg + O 2 2H 2 O  2H 2 + O 2 A. Decomposition IV. Types of Reactions

31. Practice Problems 1. H + Cl  2. NaBr  3. FeCl 3  4. Ba + N  IV. Types of Reactions

32. C. Single Replacement Reactions One element replaces a similar element in a compound. A + B X  A X + B Al + Fe (NO 3 ) 2  Fe + Al (NO 3 ) 3 2 3 3 2 IV. Types of Reactions

33. Activity Series Is a list of elements organized according to the ease with which they undergo certain chemical reactions. The elements on top are said to be more active than the elements below them. Elements on top can replace the elements below them. Li, Rb, K, Ba, Sr, Ca, Na, Mg, Al, Mn F 2, Cl 2, Br 2, I 2 IV. Types of Reactions

34. Practice!!! Will copper replace silver in silver nitrate? Mg + CuSO 4  +2 +2 -2 Cu + MgSO 4 Magnesium and Copper switch places ! Like replaces like! Cu + AgNO 3  Will this rxn occur? +2 +1 -1 Ag + Cu(NO 3 ) 2 Cu – 1 1 Ag - 1 1 NO 3 - 1 2 2 2222 2 2 YES!

35. D. Double Replacement KI + Cu(NO 3 ) 2  +1 -1 +2 -1 KNO 3 + CuI 2 K – 1 1 I – 12 Cu – 11 NO 3 -2 1 2 2 2 2 2222 IV. Types of Reactions

36. Solubility – The amount of a substance that is dissolved at solution equilibrum in a specific amount of solvent at a specified temperature. Solubility is affected by: 1.Surface area 2.Agitating solution 3.Heating a solvent – increases collisions

37. Immiscible = Substances that are not soluble in each other Miscible = are soluble in each other.

38. Solubility Rules 1.All Nitrates compd. are soluble 2. All Grp I & NH 4 compds are soluble 6.All S –2, PO 4 –3, CO 3 –2 compd are NOT SOLUBLE 3. All Chlorine compd are soluble EXCEPT: AgCl, PbCl 2, Hg 2 Cl 2 4. All Sulfate compd are soluble EXCEPT: BaSO 4, CaSO 4, PbSO 4 5.All OH compds are NOT SOLUBLE Except: Grp I & half of IIA

39. Combustion Reactions Kaboom!! A substance that combines with oxygen, releasing a large amount of energy in the form of light and heat.

40. Combustion rxns Hydrocarbon + Oxygen  Carbon dioxide & Water C x H y + O 2  CO 2 + H 2 O

41. Practice CH 4 + O 2  CO 2 + H 2 O 2 2 C11 H 42 O23 4 4444