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Seminar 7

Seminar 7. SC155. Icebreaker. What types of lightbulbs do you use in your house?. Incandescent Light Bulb. Incandescent Light Bulb. 1. Run electric current through very thin piece of Tungsten 2. Generates lots of heat along with the light 3. inefficient. Compact Fluorescent Bulb.

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Seminar 7

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  1. Seminar 7 SC155

  2. Icebreaker • What types of lightbulbs do you use in your house?

  3. Incandescent Light Bulb

  4. Incandescent Light Bulb 1. Run electric current through very thin piece of Tungsten 2. Generates lots of heat along with the light 3. inefficient

  5. Compact Fluorescent Bulb http://www.energystar.gov/index.cfm?c=cfls.pr_cfls_about

  6. Compact Fluorescent Bulb 1. Produce less heat and more light 2. Use less energy 3. Use mercury http://www.energystar.gov/index.cfm?c=cfls.pr_cfls_about

  7. Choosing the right bulb • a. Energy star • b. How much light you want • i. Measured in lumens • c. Right shade of light • i. Measured in K • Lower temps mean yellower light

  8. Compact Fluorescent Bulb 5. How CFL’s work a. Electric current driven though a tube containing argon and mercury vapor. b. Generates ultraviolet light that excites fluorescent coating (phosphor) on the inside if the tube. c. When phosphor electrons relax again, emit visible light d. Take more energy initially http://www.energystar.gov/index.cfm?c=cfls.pr_cfls_about

  9. CFL’s and mercury • 4 milligrams per bulb on average. • Mercury only an issue when bulbs are broken or to be disposed of. • If the mercury containing powder comes into contact with anything it must be thrown away. • Must recycle old bulbs. • CFL’s only produce 30% as much mercury waste as power plants produce to electricity for incandescent

  10. Seminar Questions • Why have some people been reluctant to adopt CFL’s in their homes and workplaces?

  11. Seminar Questions • Why have some people been reluctant to adopt CFL’s in their homes and workplaces? • What are the pros and cons of CFL’s?

  12. Seminar Questions • Why have some people been reluctant to adopt CFL’s in their homes and workplaces? • What are the pros and cons of CFL’s? • What are the pros and cons of incandescent bulbs?

  13. Seminar Questions • Why have some people been reluctant to adopt CFL’s in their homes and workplaces? • What are the pros and cons of CFL’s? • What are the pros and cons of incandescent bulbs? • How are CFL’s disposed of properly? Incandescent?

  14. Seminar Questions • Why have some people been reluctant to adopt CFL’s in their homes and workplaces? • What are the pros and cons of CFL’s? • What are the pros and cons of incandescent bulbs? • How are CFL’s disposed of properly? Incandescent? • Do you believe CFL’s will overtake Incandescent bulbs in popularity?

  15. Redox Practice • In each of the following equations, indicate the element that has been oxidized and the one that has been reduced. You should also label the oxidation state of each before and after the process: • 1) 2 Na + FeCl2 2 NaCl + Fe

  16. Redox Practice • In each of the following equations, indicate the element that has been oxidized and the one that has been reduced. You should also label the oxidation state of each before and after the process: • 1) 2 Na + FeCl2 2 NaCl + Fe • Sodium is oxidized, going from a 0 to +1 oxidation state. • Iron is reduced, going from a +2 to 0 oxidation state.

  17. Redox Practice • In each of the following equations, indicate the element that has been oxidized and the one that has been reduced. You should also label the oxidation state of each before and after the process: • 1) 2 Na + FeCl2 2 NaCl + Fe • 2) 2 C2H2 + 5 O2 4 CO2 + 2 H2O

  18. Redox Practice • In each of the following equations, indicate the element that has been oxidized and the one that has been reduced. You should also label the oxidation state of each before and after the process: • 1) 2 Na + FeCl2 2 NaCl + Fe • 2) 2 C2H2 + 5 O2 4 CO2 + 2 H2O • Carbon is oxidized, going from a –1 to +4 oxidation state. • Oxygen is reduced, going from a 0 to –2 oxidation state.

  19. Redox Practice • In each of the following equations, indicate the element that has been oxidized and the one that has been reduced. You should also label the oxidation state of each before and after the process: • 1) 2 Na + FeCl2 2 NaCl + Fe • 2) 2 C2H2 + 5 O2 4 CO2 + 2 H2O • 3) 2 PbS + 3 O2 2 SO2 + 2 PbO

  20. Redox Practice • In each of the following equations, indicate the element that has been oxidized and the one that has been reduced. You should also label the oxidation state of each before and after the process: • 1) 2 Na + FeCl2 2 NaCl + Fe • 2) 2 C2H2 + 5 O2 4 CO2 + 2 H2O • 3) 2 PbS + 3 O2 2 SO2 + 2 PbO • Sulfur is oxidized, going from a –2 to +4 oxidation state. • Oxygen is reduced, going from a 0 to –2 oxidation state.

  21. Redox Practice • In each of the following equations, indicate the element that has been oxidized and the one that has been reduced. You should also label the oxidation state of each before and after the process: • 1) 2 Na + FeCl2 2 NaCl + Fe • 2) 2 C2H2 + 5 O2 4 CO2 + 2 H2O • 3) 2 PbS + 3 O2 2 SO2 + 2 PbO • 4) 2 H2 + O2 2 H2O

  22. Redox Practice • In each of the following equations, indicate the element that has been oxidized and the one that has been reduced. You should also label the oxidation state of each before and after the process: • 1) 2 Na + FeCl2 2 NaCl + Fe • 2) 2 C2H2 + 5 O2 4 CO2 + 2 H2O • 3) 2 PbS + 3 O2 2 SO2 + 2 PbO • 4) 2 H2 + O2 2 H2O • Hydrogen is oxidized, going from a 0 to +1 oxidation state. • Oxygen is reduced, going from a 0 to –2 oxidation state.

  23. Redox Practice • In each of the following equations, indicate the element that has been oxidized and the one that has been reduced. You should also label the oxidation state of each before and after the process: • 1) 2 Na + FeCl2 2 NaCl + Fe • 2) 2 C2H2 + 5 O2 4 CO2 + 2 H2O • 3) 2 PbS + 3 O2 2 SO2 + 2 PbO • 4) 2 H2 + O2 2 H2O • 5) Cu + HNO3 CuNO3 + H2 • Copper is oxidized, going from a 0 to +1 oxidation state. • Hydrogen is reduced, going from a +1 to 0 oxidation state.

  24. Redox Practice • In each of the following equations, indicate the element that has been oxidized and the one that has been reduced. You should also label the oxidation state of each before and after the process: • 1) 2 Na + FeCl2 2 NaCl + Fe • 2) 2 C2H2 + 5 O2 4 CO2 + 2 H2O • 3) 2 PbS + 3 O2 2 SO2 + 2 PbO • 4) 2 H2 + O2 2 H2O • 5) Cu + HNO3 CuNO3 + H2 • 6) AgNO3 + Cu  CuNO3 + Ag

  25. Redox Practice • In each of the following equations, indicate the element that has been oxidized and the one that has been reduced. You should also label the oxidation state of each before and after the process: • 1) 2 Na + FeCl2 2 NaCl + Fe • 2) 2 C2H2 + 5 O2 4 CO2 + 2 H2O • 3) 2 PbS + 3 O2 2 SO2 + 2 PbO • 4) 2 H2 + O2 2 H2O • 5) Cu + HNO3 CuNO3 + H2 • 6) AgNO3 + Cu  CuNO3 + Ag  • Copper is oxidized, going from a 0 to +1 oxidation state. • Silver is reduced, going from a +1 to 0 oxidation state.

  26. Titration Practice • Find the requested quantities in the following problems: • 1) If it takes 54 mL of 0.1 M NaOH to neutralize 125 mL of an HCl solution, what is the concentration of the HCl?

  27. Titration Practice • Find the requested quantities in the following problems: • 1) If it takes 54 mL of 0.1 M NaOH to neutralize 125 mL of an HCl solution, what is the concentration of the HCl? Because NaOH and HCl are in a 1:1, you can use M1V1 = M2V2­ (54 mL NaOH)(0.1 M NaOH) = (125 mL HCl)(M HCl) M HCl =0.043 M HCl

  28. Titration Practice • Find the requested quantities in the following problems: • 1) If it takes 54 mL of 0.1 M NaOH to neutralize 125 mL of an HCl solution, what is the concentration of the HCl? • 2) If it takes 25 mL of 0.05 M HCl to neutralize 345 mL of NaOH solution, what is the concentration of the NaOH solution?

  29. Titration Practice • Find the requested quantities in the following problems: • 1) If it takes 54 mL of 0.1 M NaOH to neutralize 125 mL of an HCl solution, what is the concentration of the HCl? • 2) If it takes 25 mL of 0.05 M HCl to neutralize 345 mL of NaOH solution, what is the concentration of the NaOH solution? Because NaOH and HCl are in a 1:1, you can use M1V1 = M2V2­ (25 mL HCl)(0.05 M HCl) = (345 mL NaOH)(M NaOH) M NaOH=0.0036 M NaOH

  30. Titration Practice • Find the requested quantities in the following problems: • 3) If it takes 50 mL of 0.5 M KOH solution to completely neutralize 125 mL of sulfuric acid solution (H2SO4), what is the concentration of the H2SO4 solution? KOH + H2SO4 K2SO4 + 2H2O

  31. Titration Practice • Find the requested quantities in the following problems: • 3) If it takes 50 mL of 0.5 M KOH solution to completely neutralize 125 mL of sulfuric acid solution (H2SO4), what is the concentration of the H2SO4 solution? KOH + H2SO4 K2SO4 + 2H2O For problem 3, you need to divide your final answer by two, because H2SO4 is a diprotic acid, meaning that there are two acidic hydrogens that need to be neutralized during the titration. As a result, it takes twice as much base to neutralize it, making the concentration of the acid appear twice as large as it really is. use M1V1 = M2V2­ [(50 mL KOH)(0.5 M KOH)]/2 = (125 mL H2SO4)(M H2SO4) M H2SO4=0.1 M H2SO4

  32. Titration Practice • Find the requested quantities in the following problems: • 4) Can I titrate a solution of unknown concentration with another solution of unknown concentration and still get a meaningful answer? Explain your answer in a few sentences.

  33. Titration Practice • Find the requested quantities in the following problems: • 4) Can I titrate a solution of unknown concentration with another solution of unknown concentration and still get a meaningful answer? Explain your answer in a few sentences. • You cannot do a titration without knowing the molarity of at least one of the substances, because you’d then be solving one equation with two unknowns (the unknowns being M1 and M2).

  34. Titration Practice • Find the requested quantities in the following problems: • 5) Explain the difference between an endpoint and equivalence point in a titration.

  35. Titration Practice • Find the requested quantities in the following problems: • 5) Explain the difference between an endpoint and equivalence point in a titration. • Endpoint: When you actually stop doing the titration (usually, this is determined by a color change in an indicator or an indication of pH=7.0 on an electronic pH probe) • Equivalence point: When the solution is exactly neutralized. It’s important to keep in mind that the equivalence point and the endpoint are not exactly the same because indicators don’t change color at exactly 7.0000 pH and pH probes aren’t infinitely accurate. Generally, you can measure the effectiveness of a titration by the closeness of the endpoint to the equivalence point.

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