AQA CHEM2 ~ May 23rd 2012 ~ AS Chemistry

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Yeah, along with CHEM4. Did you finish that in January? PM me if you ever want to exchange 'questions' and general help. :smile:

Yeah I'm resetting chem 4 as I got a B :angry:

Sure that'd be cool after this exam sometime :smile:

Reply 1781

Jack_Smith

Original post by hus11128386

yh but how do u know exctly.. jus experiment wid diff numbers of C's and H's?

yeahh..thats what i did :/ why is there some specific way?

Reply 1782

blitzle

Does anyone have the January 2012 paper and mark scheme? :smile:

Reply 1783

hus11128386

Original post by Jack_Smith

yeahh..thats what i did :/ why is there some specific way?

i dunno, dats y i wo askin u, lol.......so i dont waste time in exam..experimentin wid diff numers nd can get num formula quicker

Reply 1784

Jack_Smith

can some one explain what happens when there is excess chlorine in free radical substitution

Reply 1785

Jack_Smith

Original post by hus11128386

i dunno, dats y i wo askin u, lol.......so i dont waste time in exam..experimentin wid diff numers nd can get num formula quicker

well i dont think there is any other way, but even guessing this wont take much time

Reply 1786

cheesecake11

Original post by Jack_Smith

can some one explain what happens when there is excess chlorine in free radical substitution

further propagnation occurs, ie with methane and chlorine
ch3cl + cl*----> Hcl + ch2cl*
ch2cl* + cl2 -----> ch2cl2 + cl*

Reply 1787

PhoenixxX

Original post by Jack_Smith

can some one explain what happens when there is excess chlorine in free radical substitution

Further substitutions happen and you get products like di/tri/tetrachloromethane. Adding excess methane is a way to prevent this from happening, and get the targeted chloromethane :smile:

I think...

Reply 1788

Natty.B

good luck today, hopefully we get a nice paper

Reply 1789

R10T_N0_B0UNTY

Any body have any tips on when to state the actual temperatures.... for example if they ask what are the conditions???
Is simply stating High Temperatures sufficient or do you have to state the degrees as well
Thanks :smile:

Reply 1790

puresse

do we need to know about the observations for the reaction between sulfuric acid and NaX
- X being a halide ion?

Reply 1791

hus11128386

Original post by puresse

do we need to know about the observations for the reaction between sulfuric acid and NaX
- X being a halide ion?

OMG yes, and you have to know all equations aswell.. wil u b able to learn it and rem it 4 test?

Reply 1792

berryripple

Anyone else on the coffee?

:coffee:

Reply 1793

hus11128386

What is the halide that forms cream ppt with silver nitrate.

I thought Cl= white ppt
Br- cream ppt
I- yellow ppt

but question in jun 11 and mark scheme says its NaCl. wtf?

Reply 1794

hus11128386

Original post by hus11128386

What is the halide that forms cream ppt with silver nitrate.

I thought Cl= white ppt
Br- cream ppt
I- yellow ppt

but question in jun 11 and mark scheme says its NaCl. wtf?

my mistake... dint read question prop.. it was askin to identify other sodium halide that must be present in the mixture of the two sodium halides (2 given were Br and I)

So other one is NaCl.

I get it.. lol, dint read question prp.

Reply 1795

MasterYoda

Original post by hus11128386

What is the halide that forms cream ppt with silver nitrate.

I thought Cl= white ppt
Br- cream ppt
I- yellow ppt

but question in jun 11 and mark scheme says its NaCl. wtf?

read the question they did the test one after the other. If you think about it white + yellow = cream so there was a cream precipitate and once the dilute ammonia was added one of them dissolved. we know Chlorine dissolves in dilute ammonia therefore the answers NaCl..... I think..

Reply 1796

Mocking_bird

Time to stroll through my checklist :sleep:

Reply 1797

Tealeaves

do we need to know all the state symbols for all the equations for the extraction of metals?

Reply 1798

Jack_Smith

definition of biofuel?

Reply 1799

puresse

Original post by hus11128386

OMG yes, and you have to know all equations aswell.. wil u b able to learn it and rem it 4 test?

i know the equations but hate it when they ask for the observations

H2S - smell of bad eggs?
S - yellow solid / ppt
HBr HI HCl- misty fumes
Br2 brown fumes ?
I2 - brown solution black ppt ?

are these correct and is there any more we need to know