Topics for Today CFCs and the Ozone Hole The Cl. Radical Properties and Uses of CFCs! “We’ve got Styrofoam boxes for the ozone layer”

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Presentation transcript:

Topics for Today CFCs and the Ozone Hole The Cl. Radical Properties and Uses of CFCs! “We’ve got Styrofoam boxes for the ozone layer”

Readings for Today Review 2.9 CFCs: Properties, uses and interactions with ozone 2.11 Responses to a global concern 2.12 Looking to the future

Topics for Friday What can we do about the ozone hole (Part 1)? Quiz #6!!

Readings for Friday Just review sections 2.11 and 2.12

Announcements!!

Announcements!! - a This weeken d!

Announcements!! Exam #2 next Friday (the 16 th ) Same deal as last time…

Announcements!! Exam #2 next Friday (the 16 th ) Same deal as last time… Non- memory calculators OK. Please sit in dark seats Exams will be handed out at the door (at 8:35) Periodic Table will be attached…

Topics for Today CFCs and the Ozone Hole The Cl. Radical Properties and Uses of CFCs! “We’ve got Styrofoam boxes for the ozone layer”

REVIEW CCl 2 F 2 λ < 220 nm UV-C light. CClF 2 +Cl. Only in the stratosphere

What’s so bad about the Cl. radical?

First Problem…

PSCs 1) Over the winter, chemicals in the stratosphere (including pollutants) get trapped in the PSC’s.

Next, when spring arrives…

PSCs 3) In the spring (October), the clouds melt and the chemicals (like Cl. ) are released.

Cl... +O3O3 ClO. O2O2 + Cl. destroys ozone

Cl... +O3O3 ClO. O2O2 + Cl. destroys ozone Be able to draw this Lewis Structure!!

As if this wasn’t enough…

ClO + ClO ClOOCl ClO + ClO ClOOCl ClOOCl ClOO + Cl ClOOCl ClOO + Cl ClOO Cl + O 2 ClOO Cl + O 2 UV Cl. gets regenerated! ! No need to memorize this set of equations…

Cl... +O3O3 ClO. O2O2 + ClO + ClO ClOOCl ClO + ClO ClOOCl ClOOCl ClOO + Cl ClOOCl ClOO + Cl ClOO Cl + O 2 ClOO Cl + O 2 UV No need to memorize this set of equations…

Cl... +O3O3 ClO. O2O2 + ClO + ClO ClOOCl ClO + ClO ClOOCl ClOOCl ClOO + Cl ClOOCl ClOO + Cl ClOO Cl + O 2 ClOO Cl + O 2 UV No need to memorize this set of equations…

Cl... +O3O3 ClO. O2O2 + ClO + ClO ClOOCl ClO + ClO ClOOCl ClOOCl ClOO + Cl ClOOCl ClOO + Cl ClOO Cl + O 2 ClOO Cl + O 2 UV No need to memorize this set of equations… ETC…

Cl... +O3O3 ClO. O2O2 + ClO + ClO ClOOCl ClO + ClO ClOOCl ClOOCl ClOO + Cl ClOOCl ClOO + Cl ClOO Cl + O 2 ClOO Cl + O 2 UV No need to memorize this set of equations… 2O 3 3O 2 ETC… NET destruction of ozone!!

How do CFCs get into the atmosphere? FREON-12 (dichlorodifluoromethane) C Cl F F trichlorofluoromethane C Cl F

Uses of CFCs Why were CFCs used in the first place?

Properties of CFCs nontoxic nontoxic colorless, odorless, tasteless colorless, odorless, tasteless not flammable not flammable inert inert What have they been used for?

Uses of CFCs Refrigerants!

Refrigeration History…

1931 Freon -12 (DuPont) introduced as a refrigerant in commercial refrigerators. What did CFCs replace?

H H H N Ammonia, NH 3 AND Sulfur Dioxide, SO 2

NAAQS

1931 General Motors's Frigidaire replaces ammonia with Freon 12 refrigerant gas, making refrigerators safe for households around the industrialized world. History Channel Timeline

Uses of CFCs Foaming Agents! Styrofoam® C = C H HH Styrene 6

Uses of CFCs Propellants!

Uses of CFCs Fire Suppressant s!

One thing that no one ever thought to ask…

How are CFCs removed from the atmosphere? FREON-12 (dichlorodifluoromethane) C Cl F F trichlorofluoromethane C Cl F

How are other air pollutants removed from the atmosphere?

1. Light

+ NO 2 + O.O. NO Visible light ~600 nm Visible light ~600 nm

How are air pollutants removed from the atmosphere? 1. Light 2. Washed out by the rain

Acid Rain H+H+ SO 4 2- H+H+ H+H+ SO 3 2- H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ SO 4 2- H+H+ H+H+ SO 3 2- H+H+ H+H+ SO 4 2- H+H+ H+H+ H+H+ H+H+ SO 3 2- H+H+

How are air pollutants removed from the atmosphere? 1. Light 2. Washed out by the rain 3. “React Away”

ozone Ozone Destroys Rubber and Plants

How are CFCs removed from the atmosphere? FREON-12 (dichlorodifluoromethane) C Cl F F trichlorofluoromethane C Cl F

How are CFCs removed from the atmosphere? 1. Light?

CCl 2 F 2 λ < 220 nm UV-C light. CClF 2 +Cl. Only up in the stratosphere

How are CFCs removed from the atmosphere? 1. Light? NO 2. Washed out by the rain?

DETOUR

REVIEW Electronegativity! An atom’s “greediness” for electrons.

Covalent Bonds O=C=O C H H H H C H H H H ::. O::OC:: A bond where two atoms share electrons.. methane, CH 4 carbon dioxide, CO 2 Not all covalent bonds are created equal!!!

COVALENT BONDS NONPOLARPOLAR

TYPES OF BONDS Electronegativity Difference LowHigh IONICPOLARNONPOLAR COVALENT

Polar Bonds: Unequal sharing of electrons in a chemical bond. Still a covalent bond! RESULTS IN AN UNEQUAL DISTRIBUTION OF CHARGE!!

HCl EN H Cl High difference in EN! HCl is a polar bond! δ-δ- δ+δ+ Read as “delta minus” Means “slightly negative”

H — Cl or H :Cl H — Cl or H :Cl Unequal sharing of 2 electrons by 2 atoms

HCl C H H H H EN H Cl C High difference in EN! HCl is a polar bond! δ-δ- δ+δ+ What about methane ? The C-H bond is nonpolar!

C H H H H ::. The electrons are shared (relatively) equally by the two atoms H = 2.1 C = 2.5 The C-H bond is nonpolar!

Hydrocarbons Contain only hydrogen and carbon… C C H H H Ethane, C 2 H 6 H H H Polar or nonpolar bonds? H = 2.1 C = 2.5 Polar or nonpolar molecule ?

H H H N Ammonia, NH 3 δ-δ-δ-δ- δ+δ+δ+δ+ δ+δ+δ+δ+ δ+δ+δ+δ+ H = 2.1 N = 3.0 Polar or nonpolar bonds? Polar or nonpolar molecule ? Look at the SHAPE! !

Water O — H H Polar or nonpolar bonds? δ-δ-δ-δ- δ+δ+δ+δ+ δ+δ+δ+δ+ H = 2.1 O = 3.5 Polar or nonpolar molecule ?

Ammonia Fountain!! Is ammonia soluble in water? NH 3 +H2OH2ONH 4 OH Ammonium Ion, NH 4 + Hydroxide Ion, OH -

“LIKE DISSOLVES LIKE”

That is… Polar compounds are soluble in polar compound Nonpolar compounds in nonpolar compounds Polar compounds are usually NOT soluble in nonpolar compounds.

END DETOUR

How are CFCs removed from the atmosphere? 1. Light? NO 2. Washed out by the rain?

FREON-12 (dichlorodifluoromethane) C Cl F F C = 2.5 Cl = 3.0 F = 4.0 Polar or nonpolar bonds? δ-δ-δ-δ- δ-δ-δ-δ- δ-δ-δ-δ- δ-δ-δ-δ- δ+δ+δ+δ+ Polar or nonpolar molecule ? So, are CFCs washed out by the rain?

How are air pollutants removed from the atmosphere? 1.Light? NO 2. Washed out by the rain? NO 3. “React Away”

Properties of CFCs nontoxic nontoxic colorless, odorless, tasteless colorless, odorless, tasteless not flammable not flammable inert inert They persist in the environment for long periods of time!

“Once CFCs get into the atmosphere, they are virtually indestructible.” That is, they really don’t react with anything…

Dichlorodifluoromethane 120 years

Trichlorofluoromethane 60 years

~90% of all the CFCs ever produced are still in the atmosphere!