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CHEMICAL EQUATIONS

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CHEMICAL EQUATIONS

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    1. CHEMICAL EQUATIONS 1

    2. Water and what is known from its equation. 2

    3. CHEMICAL REACTIONS one or more substances are changed into different substances Represented by chemical equations 2H2 (g) + O2(g) ? 2H2O(g) ?REACTANTS PRODUCTS ? 3

    4. Show the substances undergoing change and the result(s). Show relative amts. of elements/cmpds. that take part in the changes [coefficients] See ‘Symbols Used in Chem. Rxn. handout CHEMICAL EQUATIONS 4

    5. Writing Chemical Equations 5

    6. 6

    7. Writing Chemical Equations iron + oxygen ? iron(III) oxide 7 Three common chemical reactions are shown. a) When methane gas burns, it combines with oxygen to form carbon dioxide and water. b) Iron turns to red-brown rust (iron(III) oxide) in the presence of oxygen in the air. c) Hydrogen peroxide decomposes to water and oxygen when used as an antiseptic.Three common chemical reactions are shown. a) When methane gas burns, it combines with oxygen to form carbon dioxide and water. b) Iron turns to red-brown rust (iron(III) oxide) in the presence of oxygen in the air. c) Hydrogen peroxide decomposes to water and oxygen when used as an antiseptic.

    8. Writing Chemical Equations Hydrogen Peroxide ? Water and Oxygen 8 Three common chemical reactions are shown. a) When methane gas burns, it combines with oxygen to form carbon dioxide and water. b) Iron turns to red-brown rust (iron(III) oxide) in the presence of oxygen in the air. c) Hydrogen peroxide decomposes to water and oxygen when used as an antiseptic.Three common chemical reactions are shown. a) When methane gas burns, it combines with oxygen to form carbon dioxide and water. b) Iron turns to red-brown rust (iron(III) oxide) in the presence of oxygen in the air. c) Hydrogen peroxide decomposes to water and oxygen when used as an antiseptic.

    9. The PVC Method to WRITING A BALANCED CHEMICAL EQUATION 9

    10. WRITING A BALANCED CHEMICAL EQUATION Tips: Start with element that appears only once on each side. Save oxygen and hydrogen for last 10

    11. Lithium aluminum hydride reacts with water to produce lithium hydroxide, aluminum hydroxide and hydrogen gas. LiAlH4 + H2O ? LiOH + Al(OH)3 + H2 LiAlH4 + 4H2O ? LiOH + Al(OH)3 + H2 LiAlH4 + 4H2O ? LiOH + Al(OH)3 + 4H2 *Note that hydrogen is diatomic when not bonded to other elements. 11

    12. Diatomic Molecules Harvey BrOFINCl 12

    13. Persistent difficulty ? Check all FORMULAS to make sure they are correct K2(SO4) v K2(SO3) 13

    14. Ammonia reacts with oxygen gas to produce nitrogen dioxide and water. NH3 + O2 ? NO2 + H2O 2NH3 + O2 ? NO2 + 3H2O 2NH3 + O2 ? 2NO2 + 3H2O 2NH3 + 7/2O2 ? 2NO2 + 3H2O 4NH3 + 7O2 ? 4NO2 + 6H2O 14

    15. Synthesis 15

    16. Common Types of Chemical Reactions Synthesis two or more simple compounds combine to form a more complicated one General form : A + B ---> AB Iron and sulfur to form iron (II) sulfide: 8 Fe + S8 ---> 8 FeS 16

    17. Decomposition 17

    18. Common Types of Chemical Reactions Decomposition opposite of a synthesis reaction complex molecule breaks down to make simpler ones General form: AB ---> A + B Hydrogen peroxide decomposes to water and oxygen gas: H2O2 ? H2O +O2 18

    19. Single Replacement 19

    20. Common Types of Chemical Reactions Single Replacement one element trades places with another element in a compound General form: A++ BC ---> AC + B, or A- + BC ---> BA + C Zinc replaces copper in copper sulfide solution: Zn + CuSO4 ? ZnSO4 + Cu 20

    21. Double Replacement 21

    22. Common Types of Chemical Reactions Double Replacement cations (positive ions) of two different molecules switch places, forming two entirely different compounds General form: AB + CD ---> AD + CB Sodium Chloride (salt) solution reacts with silver nitrate to produce silver chloride and sodium nitrate. NaCl +AgNO3 ? AgCl + NaNO3 22

    23. 23

    24. Common Types of Chemical Reactions Combustion oxygen combines with a compound containing carbon, hydrogen and sometimes oxygen forms water and carbon dioxide. General Form: CxHy ? CO2 + H2O Exothermic Burning of naphthalene: C10H8 + 12 O2 ---> 10 CO2 + 4 H2O 24

    25. Review and Foreshadow Video Logic and rules for balancing chemical equations are reviewed Types of chemical reactions are introduced Take Notes Quiz (10 points) @ end of video Name Period Number 1-10 25

    26. Decomposition: Special Cases Anions and cations do not separate as expected. X = any metal 26

    27. Metal carbonates XCO3 ? XO + CO2 metal oxide & carbon dioxide CaCO3 ? CaO + CO2 27

    28. Metal hydroxides XOH ? XO + H2O metal oxide & water Ca(OH)2 ? CaO + H2O 28

    29. Metal chlorates XClO3 ? XCl + O2 metal chloride & oxygen gas Ca(ClO3)2 ? CaCl2 + 3O2 29

    30. Single Replacement Reactions A++ BC ---> AC + B, or A- + BC ---> BA + C Are the free elements always able to replace the element in the compound? How can we tell when / if the free elements will successfully replace the element in the compound? 30

    31. Activity Series [partial listing] 31

    32. Will these reactions occur? ZnCO3 + H2 ?? ZnCO3 + H2 ?N.R. AgCl + Mg ?? 2AgCl + Mg ?MgCl2 + 2Ag 32

    33. Replacing HYDROGEN in WATER Water is unusually stable. Replacing the hydrogen in water depends on: Placement of free element on activity series, and TEMPERATURE 33

    34. Replacing HYDROGEN in WATER < 175 oC X + H2O ? XOH + H2 Metal hydroxide hydrogen gas Ca + 2H2O ? Ca(OH)2 + H2 > 175oC X + H2O ? XO + H2 Metal oxide hydrogen gas Ca + H2O ? CaO + H2 34

    35. Double Replacement Reactions AB + CD ---> AD + CB When a double replacement reaction occurs one of the following are produced: gas precipitate an insoluble solid that forms when two liquids are mixed water These rxn also called acid-base rxn 35

    36. SOLUBILITY The property of a substance to dissolve Water Universal solvent Solubility Table - handout NaCl + AgNO3 ? NaNO3 + AgCl 2NaCl + Fe(NO3)2 ? 2NaNO3 + FeCl2 ? NR (no double replacement products made) 36

    37. Predicting Reaction Products Analyze the reactants. Decide what pattern of chemical reaction the reactants will fit. Na and H2SO4 a single element and a compound fit the single replacement pattern. H2 and O2 two elements fit the synthesis pattern. 37

    38. Use the pattern to decide which elements will go together. [REMEMBER to refer to the Activity Series for single replacement reactions.] Na + H2SO4 ? Na replaces H [Na stronger than H]; H becomes lone element. 2Na + H2SO4 ? Na2SO4 + H2 38

    39. Use valences to form good chemical formulas to represent the products. The sum of the valences equals zero in a chemical formula. Na+1; SO4-2 2Na + H2SO4 ? Na2SO4 + H2 Write the diatomic elements as H2, Br2, O2, F2, I2, N2, and Cl2. when they are by themselves.. (Henry BrOFINCl) 2H2 + O2 ? 2H2O 39

    40. Balance the equations using coefficients (BIG numbers placed in FRONT of the chemical formula.) 2Na + H2SO4 ? Na2SO4 + H2 2H2 + O2 ? 2H2O Balance H, O last. 40

    41. Nuclear Equations Nuclear equations result in the change of one element into another transmutation 238 number of protons + neutrons 92 U number of protons (determines identity of atom) 41

    42. 42

    43. a particle decay 238 234 4 92 U ? 90 Th + 2He thorium a particle 43

    44. ß particle decay 234 234 0 90 Th ? 91 Pa + -1e- protactinium ß particle Decay continues until a stable substance is reached. 44

    45. K capture decay 100 0 100 46 Pd + -1e- ? 45 Rh 45

    46. Rules for balancing nuclear equations The sum of the mass numbers (top) is the same on both sides of the equation. The sum of the electric charges (bottom) is the same on both sides of the equation. 46

    47. Find the unknown product 18 0 9F ? +1 e- + ? Find the mass 18 = 0 + x 18 = x 18 0 18 9 F ? + 1e- + ? 47

    48. 230?V X Find the charge 9 = 1 + x 8 = x 18 0 18 9F ? +1e- + 8 ? 48

    49. Find the element 18 0 18 9F ? +1e- + 8 O 49

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