Seminar 7 SC155. Icebreaker What types of lightbulbs do you use in your house?

Seminar 7SC155

IcebreakerWhat types of lightbulbs do you use in your

house?

Incandescent Light Bulb

Incandescent Light Bulb1. Run electric current through very thin piece of Tungsten2. Generates lots of heat along with the light3. inefficient

Compact Fluorescent Bulb

http://www.energystar.gov/index.cfm?c=cfls.pr_cfls_about



1. Produce less heat and more light2. Use less energy3. Use mercury

Choosing the right bulb

a. Energy starb. How much light you want

i. Measured in lumensc. Right shade of light

i. Measured in Kii. Lower temps mean

yellower light



5. How CFL’s worka. 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

CFL’s and mercury4 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

Seminar QuestionsWhy have some people been reluctant to

adopt CFL’s in their homes and workplaces?


adopt CFL’s in their homes and workplaces?What are the pros and cons of CFL’s?


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?



bulbs?How are CFL’s disposed of properly?

Incandescent?



bulbs?How are CFL’s disposed of properly?

Incandescent?Do you believe CFL’s will overtake

Incandescent bulbs in popularity?

Redox PracticeIn 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.




2) 2 C2H2 + 5 O2 4 CO2 + 2 H2O




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.




2) 2 C2H2 + 5 O2 4 CO2 + 2 H2O

3) 2 PbS + 3 O2 2 SO2 + 2 PbO




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.





2) 2 C2H2 + 5 O2 4 CO2 + 2 H2O

3) 2 PbS + 3 O2 2 SO2 + 2 PbO

4) 2 H2 + O2 2 H2O




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.


Redox PracticeIn 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:


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.




2) 2 C2H2 + 5 O2 4 CO2 + 2 H2O

3) 2 PbS + 3 O2 2 SO2 + 2 PbO

4) 2 H2 + O2 2 H2O


6) AgNO3 + Cu CuNO3 + Ag

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:


2) 2 C2H2 + 5 O2 4 CO2 + 2 H2O

3) 2 PbS + 3 O2 2 SO2 + 2 PbO

4) 2 H2 + O2 2 H2O


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.

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



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?



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


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


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


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.


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).


5) Explain the difference between an endpoint and equivalence point in a titration.


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.

Seminar 7 SC155. Icebreaker What types of lightbulbs do you use in your house?

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