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CH110 Chapter 5 Chemical Reactions

CH110 Chapter 5 Chemical Reactions. Moles Chemical Changes Chemical Equations Types of Reactions Oxidation-Reduction Energy in Chemical Reactions Reaction Rates. The Mole. 2. 1 pair = 1 dozen = 1 mole =. 12. 6.02 x 10 23. 602,000,000,000,000,000,000,000. 1 mol eggs___

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CH110 Chapter 5 Chemical Reactions

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  1. CH110 Chapter 5Chemical Reactions • Moles • Chemical Changes • Chemical Equations • Types of Reactions • Oxidation-Reduction • Energy in Chemical Reactions • Reaction Rates

  2. The Mole 2 1 pair = 1 dozen = 1 mole = 12 6.02 x 1023 602,000,000,000,000,000,000,000. 1 mol eggs___ 6.02 x 1023eggs 1 mol Au_______ 6.02 x 1023 Au atoms _____1 mole H2O_____ 6.02 x 1023 H2O molecules

  3. The Mole & Molecular Weight (Mass) 1 mole = MW in g’s 1 mole S = 32 g S 1 mol S_ 32 g S 32 g S 1 mol S 1 mole C = 12 g C 1 mol C 12 g C 12 g C 1 mol C

  4. Molecular Weight (Mass) Find the MW of Glucose; C6H12O6 6 mol C 1 12.0 g C = 1 mol C 72.0 g C 12.0 g H 12 mol H 1 1.0 g H = 1 mol H 96.0 g O 6 mol O 1 16.0 g O = 1 mol O 180.0 g C6H12O6 1 mol C6H12O6

  5. What is Chemistry? • “The study of Matter and its Changes.” Physical Changes= Changes in a Physical Property • Appearance: • melting, freezing, evaporation… • stretching, molding, cutting… Chemical Changes = Changes in a Chemical Property Chemical Composition:

  6. Chemical Changes • Change in the Chemical Composition Examples: Burning of Magnesium Rusting of Iron Decomposing of wood Souring of Milk

  7. Chemical Reactions • Gas formed • Solid precipitate formed • Color change • Temperature Change • Gives heat = exothermic • Gets cold = endothermic

  8. Chemical Reactions • Shows how the Chemical change occurs. Reactants Products  C3H8 + O2 CO2 + H2O + Energy Mg + O2 MgO + Energy Fe + O2 Fe2O3

  9. Chemical equations Chemist’s shorthand to describe a reaction. heat 2 H2 + O2 2 H2O + E (g) (g) (g) • Reactants • Products • The state of all substances (g) (l) (s) (aq) • Any conditions used in the reaction • Same # & type atoms on each side • Law of Conservation of Matter

  10. Balancing Equations Making Hot dogs: How many packages wieners & buns to buy so none is left over. 3 2 24 ___W8 + ___B12 ___WB • Reactants • Products http://www.youtube.com/watch?v=oYIHLUxzRr8

  11. Balancing Equations Na3PO4 + MgCl2Mg3(PO4)2 + NaCl • Reactants • Products 3 1 4 1 2 Na P O Mg Cl 1 2 8 3 1 Step 1: Count atoms of each element on both sides of equation.

  12. Balancing Equations Na3PO4 + MgCl2Mg3(PO4)2 + NaCl • Reactants • Products 3 1 4 1 2 Na P O Mg Cl 1 2 8 3 1 - not balanced - not balanced - not balanced - not balanced - not balanced Step 2: Determine which atoms are not balanced.

  13. Balancing Equations Na3PO4 + MgCl2Mg3(PO4)2 + NaCl • Reactants • Products 3 1 4 1 2 Na P O Mg Cl 1 2 8 3 1 - not balanced - not balanced - not balanced - not balanced - not balanced Step 3: Balance elements with #’s in front of formulas until all balanced. (Never change the formulas!)

  14. Balancing Equations 2 3 1 6 Na3PO4 + MgCl2Mg3(PO4)2 + NaCl • Reactants • Products 3 1 4 1 2 Na P O Mg Cl 1 2 8 3 1 - not balanced 6 6 - not balanced 2 - not balanced 8 - not balanced 3 - not balanced 6 6 • Hints: • Start with a metal in a complex compound, or an element that only appears in one formula. (ie Mg here)

  15. Balancing Equations C2H6 + O2CO2 + H2O • Reactants • Products C H O • Hints: • Start with an element that only appears in one formula on both sides of the equation. • Leave oxygen until last.

  16. Balancing Equations C2H6 + O2CO2 + H2O • Reactants • Products 2 6 2 C H O 1 2 3 Step 1: Count atoms of each element on both sides of equation.

  17. Balancing Equations C2H6 + O2CO2 + H2O • Reactants • Products 2 6 2 C H O 1 2 3 - not balanced - not balanced - not balanced Step 2: Determine which atoms are not balanced.

  18. Balancing Equations 3.5 2 3 C2H6 + O2CO2 + H2O • Reactants • Products 2 6 2 C H O 1 2 3 2 - not balanced - not balanced 6 - not balanced 7 5 7 Step 3: Balance one element at a time with coefficients in front of formulas until all balanced. (Never change the formula!)

  19. Balancing Equations 3.5 2 3 C2H6 + O2CO2 + H2O • Reactants • Products 2 6 2 C H O 1 2 3 2 6 7 5 7 Can’t have 3.5 O2 , so multiply equation by 2!

  20. Balancing Equations 3.5 7 4 6 2 C2H6 + O2CO2 + H2O • Reactants • Products 2 6 2 C H O 1 2 3 4 2 4 12 6 12 14 7 5 7 14 Can’t have 3.5 O2 , so multiply equation by 2!

  21. Types of Chemical Reactions Combustion Complete: C3H8 + 5O2 3CO2 + 4H2O Incomplete: 2C3H8 + 7O2 6CO + 8H2O C3H8 + 2O2 3C + 4H2O

  22. Types of Chemical Reactions Combination A + B  C Decomposition C  A + B Single Replacement: Substitution A + BX B + AX Double Replacement: Metathesis AX + BYBX + AY

  23. Combination Reactions A + B  C Explosion of Hydrogen Balloon 2H2 + O2 2H2O Rusting of Iron 4 Fe + 3 O2 2 Fe2O3 Formation of Acid Rain SO3 + H2O  H2SO4

  24. 2 H2O2 2 H2O + O2 Decomposition Reactions C  A + B Heating Egg Shells CaCO3  CaO + CO2 Blood with peroxide

  25. Single Replacement Reactions A + BX B + AX Iron Deposits on an Aluminum Pan Al + FeCl3  Fe + AlCl3

  26. potassium sodium calcium magnesium aluminum zinc chromium iron nickel tin lead Hydrogen copper silver platinum gold Activity series of metals Al + Fe+3 Fe + Al+3 Fe + H+ Fe+3 + H2 increasing reactivity Element give e’s to ion lower on list

  27. Double Replacement Reaction AX + BY  BX + AY BaCl2(aq) + Na2SO4(aq)  BaSO4(s) + 2NaCl(aq) Insoluble Precipitate Formed Ba+2Cl-1 Na+1 SO4-2

  28. Double Replacement Reaction AX + BYBX + AY • Predict the products: AgCl(s) + Mg(NO3)2(aq) 2 AgNO3(aq) + MgCl2(aq) 2 Write correct formulas then balance as needed Ag+NO3- Mg+2 Cl-

  29. Oxidation and reduction • REDOX • Where reactants exchange electrons - • Examples: • All types of batteries • alkaline, NiCad, car batteries • Rusting and corrosion • Metabolism • Antioxidants (Vit C, E prevent oxidation)

  30. Oxidation and reduction REDOX Where reactants exchange electrons - Oxidation = Losing electrons LEO: Lose Electrons Oxidation Reduction = Gaining electrons GER: Gain Electrons Reduction LEO the lion says GER

  31. Reaction Rates Fast: Oxidation: Paper burning Slow: Oxidation: Nails rusting Paper turning yellow

  32. Reaction Rates For reactants to make products: • They have to have enough E. • Molecules must collide • (solvents really help) • They have to be alignedcorrectly. (Parked cars don’t collide)

  33. 8 blocks: 34 surfaces 8 blocks: 24 surfaces Reaction Rates Factors that increase reaction rate: • More Reactants: More cars  More collisions More surface area  More collisions

  34. Reaction Rates Factors that increase reaction rate: • Higher Temperature: Faster cars  More collisions More Energy  More collisions

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