This discussion is now closed.

Check out other Related discussions

Chemistry Salters F332 june 2010

Scroll to see replies

Reply 220

username279062

Last year everyone in my sixth form got C's and D's and then retook it in Jan to get A's. It's a funny old life eh!

Reply 221

dylan2592

Anyone know why bromine is more effective at destoying ozone than Chlorine?

Reply 222

xelaman

Chlorine is more effective as it breaks down to form radicals in the stratosphere (large conc of ozone present)
Bromine breaks down in the troposphere (weaker bonding) where a lower conc of ozone is present :smile:

Reply 223

Saluki-Sake

dylan2592

Anyone know why bromine is more effective at destoying ozone than Chlorine?

Just coz it's more reactive, halogens get more reactive as you go down the group :smile:

Reply 224

Saluki-Sake

xelaman

Actually, this answers better than mine!! LOOK @ THIS ONE! :biggrin:

Reply 225

xelaman

Halogens are more reactive as you go up the group :smile:

Reply 226

Saluki-Sake

xelaman

Halogens are more reactive as you go up the group :smile:

LOL you're right!!! :p:

oops!! I was thinking of group 1 :biggrin:

Reply 227

dylan2592

xelaman

This is what I thought. But check out pg 71 of storylines book just above the yellow box on the right page. It says bromine is about 100 times more effective than chlorine.

Reply 228

kirky743

dylan2592

This is what I thought. But check out pg 71 of storylines book just above the yellow box on the right page. It says bromine is about 100 times more effective than chlorine.

Maybe it would be if it was just a bromine radical (as the radical is more reactive - though why i have no idea) and its just because bromine radicals arent found near ozone to be able to break it down.

if that makes sense.

argh chemistry why.

did anybody do the specimen paper? the advance notice questions on that have full on frightened me ah x

Reply 229

Saluki-Sake

kirky743

Aww ^_^ no I haven't, do you have a link? :smile:

Reply 230

jamiet92

Just did the Jan 2010 paper and didn't get the reagents and conditions mark. I just wondered what reagents and conditions we actually needed to know? Thanks

Reply 231

dylan2592

kirky743

I thought a chlorine radical is more reactive than a bromine radical.

Reply 232

kirky743

Saluki-Sake

Aww ^_^ no I haven't, do you have a link? :smile:

http://www.ocr.org.uk/download/assess_mat/ocr_7777_sam_gce_unit_f332.pdf <<< This is the specimen paper

http://www.ocr.org.uk/download/assess_mat/ocr_7778_sam_gce_unit_f332_adv_notice.pdf <<< this is the advance notice for the specimen paper

the last question was awful. i think this was the paper i got lowest in aha =/

Reply 233

Sreiza

kirky743

Oxidation of primary alcohol - excess potassium dichromate solution that has been acidified with weak sulphuric acid. This is distilled to form an aldehyde.

Oxidation of secondary alcohol - excess potassium dichromate etc as before. Heated under reflux to form a ketone.

Alkene ---> Alcohol : reagent is water at 70ATM pressure, 300 degrees C and in the presence of a phosphoric acid catalyst.

Hydrogenation - (alkene to alkane) -EITHER hydrogen gas at 180 degrees and 5atm pressure with a hot nickel catalyst OR room temp and pressure with a platinum catalyst

Alcohol ---> halogenoalkane - react with the acid of the halogen (HBr, HCl...)

Alcohol ---> Alkene : EITHER 180 degrees c with concentrated sulphuric acid OR hot vapour over Al2O3 at 300 degreees

Alkane ----> alkene is vapour over Al2o3

Halogenoalkane ----> amine : react with concentrated NH2 in a sealed tube

Halogenoalkane -----> Alcohol. Reflux with excess NaOH

hope that helps

if anybody finds anything incorrect in that let me know =D x

#thanks helped a lot :smile:

Reply 234

hollywoodbudgie

Hi I'm back! :angelblush:

Reply 235

jamiet92

Sreiza

#thanks helped a lot :smile:

Thanks Sreiza, thats brilliant :smile:

Reply 236

kirky743

hollywoodbudgie

Ooooh pretty o_o

Um okay!
Initation: H20---> O* + OH*
UV

Propogation: H2 + OH* ---> H2O + H*

Termination: H* + O2 ---> H2O

idk... something like that?

Where has the hydrogen gas come from? =S

And also we were told propogation needs two steps i think? :smile:

Reply 237

hollywoodbudgie

kirky743

Where has the hydrogen gas come from? =S

And also we were told propogation needs two steps i think? :smile:

It's a hydrogen radical that comes from the breaking apart of the water.
It's gas because the water is water vapour.
It's propogation because there are radicals on both sides of the equation.

God it feels good to be back :holmes:

Reply 238

kirky743

hollywoodbudgie

Noo i meant the H2. Just by two radicals bonding together?

Yeah but we were told to have to propogation steps - like when chlorine catalyses ozone breakdown and there are two parts of it( like two propogation reactions) - or is this just because a catalyst is involved here?

Thanks for your help =)