CFC's anyone??? (1 Viewer)

[angel_kate]

Hey,
Im making summaries of my notes and our teacher has left out a few things about ozone and CFCs

In section 4 of the chemical monitoring and managment syllabus:
- dot point 7: compare the properties of the gaseous forms of oxygen and the oxygen free radical.
- dot point 12: discuss the problems associated with the use of CFC's and assess the effectivness of steps taken to alleviate these problems.


If ANYONE has info about these could u please fill me in. im totally lost!
Thanks heaps

 

[quartic]

I don't know about the first point. I think there's a table comparing them in conquering chem.

OK. CFCs were basically used because they are chemically inert and are a good refrigerant. However when they are released into the atmosphere they don't break down because they are so stable so they just build up. Very slowly over decades they begin to diffuse into the stratoshere where they are subjected to short wavelength cosmic rays etc. Basically this higher energy radiation can free Cl radicals from CFCs and this sets up a chain reaction where the Cl radical can destroy hundreds of ozone molecules. I think its like this.

Cl + O3 -> ClO + O2 then
ClO + O -> Cl + O2

In this way the Cl radical isn't used up and continues to destroy ozone.

The methods used to alleviate these problems is to stop using CFCs this involves first changing over to HCFCs, which are just CFCs but with at least one hydrogen. HCFCs are less stable and can be broken down in the troposhere by reactive radicals and atoms so they don't reach the stratosphere in as high proportion.

After HCFCs are phased out they will be replaced by HFCs hydroflurocarbons. These are decomposed in the troposphere as are HCFCs and do not contain Cl atoms so do not cause the release of the Cl radical in the stratosphere.

These are long term fixes for the ozone problem as there is still a large ammount of CFCs in the troposphere which are still diffusing into the stratosphere.


For more info read several texts or at least one good one such as conquering chem. I hope that gave you some idea.

 

[stuffed4exams]

if you have the excel "Revise HSC chemistry core in a month", the oxygen ozone thing is covered well on page 116 - i just can't be bothered typing it out.
try different books though, it's covered well in conquering chem and chemistry contexts as well

 

[angel_kate]

yeah thanks, i found some in conqering chem and stuff. i still have quite a bit of time till the exam tho, so thats good
What option topic is everyone doing?
im doing forensics

 

[stuffed4exams]

Is forensics good? i wish we were doing that.
we are doing shipwrecks and salvage - dead boring - it's just electrochemistry repeated, with a few additions

 

[quartic]

Shipwrecks and salvage is the worst crap ever. The only positive is that if we get electrolysis questions in the core section they'll be a snap.

 

[angel_kate]

Yeah forensics is really good. Our teacher got us to vote on what option we wanted to do and EVERYINE voted for this, so everyone is really enjoying it, well, at least more than the other compulsory topics. lol!

 

[XRyan]

Is anyone doing the Chemistry of Art option

 

[esther]

if u need stuff for any of the 3 core topics, check out hsconline aswell... i found it pretty good
the sites www.hsc.csu.edu.au
its got a table for the oxygen and the oxygen free radical

practically most students in the state are doin shipwrecks and salvage... i HATE this topic, its so boring~!!
i just cant wait until this exam is over!! i can throw away my notes and neva hab to look at chemistry again!!!

our class voted we do forensic but our teacher said no coz there isnt many resources or someshit...

 

[angel_kate]

no way! theres actually quite a lot on forensics - it is so worth it.
i HATE chemistry but this topic is really interesting - lots of pracs playing with chemicals and flames etc!

Thanks for the website esther!

 

[superhubert]

thank god everyone hates chem... if most people do bad i wont feel as bad for not really caring...ALL HANDS ON DECK FOR THE KNOWLEDGE NATION

 

[Ronnie]

Farkennn Shipwrecks and Salvages.........

Electrolysis in aqueous conditions? Goddd how many factors do you wanna put in there? I wanna go killl someoneeeee

notice how water is oxidised and reduced differently in alkanic and acid environment....... blah I hate this option

 

[superhubert]

agreed....i'm not really even bothering to study for it. its not worth the effort.