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Edexcel Chemistry A2 Unit 5 ~ Wednesday 19th June 2013 (Now Closed)

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Hi, I have my transition metals practical assessment later this week and my revision guide isn't very helpful haha (It's the Edexcel one).

It shows a table which is very brief in its observation descriptions and simply says for excess NaOH either "soluble <colour>" or "insoluble". Then for excess NH3, it gives a few coloured ppts but for other transition metals it says "insoluble", "<colour> solution" and "soluble".

What does soluble and insoluble mean? What's the difference between soluble and a coloured solution? As well as the difference between insoluble and a coloured solution. Thank you. :smile:
Original post by LeaX
Hi, I have my transition metals practical assessment later this week and my revision guide isn't very helpful haha (It's the Edexcel one).

It shows a table which is very brief in its observation descriptions and simply says for excess NaOH either "soluble <colour>" or "insoluble". Then for excess NH3, it gives a few coloured ppts but for other transition metals it says "insoluble", "<colour> solution" and "soluble".

What does soluble and insoluble mean? What's the difference between soluble and a coloured solution? As well as the difference between insoluble and a coloured solution. Thank you. :smile:


When it says soluble, it's means that the precipitate formed while adding a few drops of either NaOH or NH3 will dissolve if more of the NaOH or NH3 is added!
Original post by James A
When it says soluble, it's means that the precipitate formed while adding a few drops of either NaOH or NH3 will dissolve if more of the NaOH or NH3 is added!


Thank you so much!
Reply 363
Avatar for jojo1995
jojo1995
2
C4H11N has several structural isomers. Write the structural formula of the isomer of C4H11N that is:

a) a primary amine with a branched chain --- i came up with ch3ch(ch3)ch2nh2 for this one which seems right :O

b) a symmetrical secondary amine with a straight chain -- absolutely couldnt do this one COULD ANYONE HELP PLEASE!!

c) a secondary amine with a branched chain

d) a tertiary amine --- THIS ONE was dodgy too- i am low on H's (this organic stuff is quite hard :s) but yeah i got (ch3)3nh3


could anyone help me out please, and also do you have any tips on approaching these DODGY questions pls :P ?
Original post by jojo1995
C4H11N has several structural isomers. Write the structural formula of the isomer of C4H11N that is:

a) a primary amine with a branched chain --- i came up with ch3ch(ch3)ch2nh2 for this one which seems right :O

b) a symmetrical secondary amine with a straight chain -- absolutely couldnt do this one COULD ANYONE HELP PLEASE!!

c) a secondary amine with a branched chain

d) a tertiary amine --- THIS ONE was dodgy too- i am low on H's (this organic stuff is quite hard :s) but yeah i got (ch3)3nh3


could anyone help me out please, and also do you have any tips on approaching these DODGY questions pls :P ?


You need to break down the information when given.

Once you do that, it's easy to approach.

(edited 11 years ago)
Reply 365
Avatar for jojo1995
jojo1995
2
Original post by James A
You need to break down the information when given.

Once you do that, it's easy to approach.



thank you so much!! yes, i think ive done it, the drawings are really helpful :biggrin:

I think the last one is ch3nh(ch3)ch2ch3 :smile:

EDIT :MY LAST ONE IS WRONG :frown: NM LOL

EDIT 2 : I GOT IT !!
its (ch3)2c2h5N
(edited 11 years ago)
Original post by jojo1995
thank you so much!! yes, i think ive done it, the drawings are really helpful :biggrin:

I think the last one is ch3nh(ch3)ch2ch3 :smile:

EDIT :MY LAST ONE IS WRONG :frown: NM LOL

EDIT 2 : I GOT IT !!
its (ch3)2c2h5N


No worries, I was doing maths in the meanwhile, so the chem was a nice break.

I'm gonna eat dinner now, I'll attempt the last one after and see if I got the same as you.
Reply 367
Avatar for mkhan51
mkhan51
Hi, I have a transition metal analysis practical next week, I'm really confused and I don't know what to look over, I've looked over the transition metals and what happens when NaOH and NH3 are added. Is that it, or should I also look over AS tests?? Thanks


Posted from TSR Mobile
Reply 368
Avatar for jojo1995
jojo1995
2
Original post by mkhan51
Hi, I have a transition metal analysis practical next week, I'm really confused and I don't know what to look over, I've looked over the transition metals and what happens when NaOH and NH3 are added. Is that it, or should I also look over AS tests?? Thanks


Posted from TSR Mobile




There is no need to look over AS work. You need to know what the transition metals behave (so colors and soluble / insoluble precipitates) in limited NH3 and NAOH and also in excess NAOH and NH3.
Reply 369
Avatar for mkhan51
mkhan51
Ok thanks


Posted from TSR Mobile
Hello all, I've got the A2 - B16 - Observation exercise on organic practical coming up very soon. Any ideas on how best to prepare? My guess is that it will involve Unit 4 organic chemistry only, but I may be wrong?
Original post by 1234lime
Hello all, I've got the A2 - B16 - Observation exercise on organic practical coming up very soon. Any ideas on how best to prepare? My guess is that it will involve Unit 4 organic chemistry only, but I may be wrong?


Mainly unit 4... but just don't forget the Benzene ring does exist :wink:
Original post by posthumus
Mainly unit 4... but just don't forget the Benzene ring does exist :wink:


great, thanks :smile:
Reply 373
Avatar for jojo1995
jojo1995
2
Does anyone know if we need to know about or carry out Kstab calculations ? :redface:
Do we need to memorise the redox equations for MnO4 titrations, Cu titrations and Chlorate titrations?
Original post by lordmackery
Do we need to memorise the redox equations for MnO4 titrations, Cu titrations and Chlorate titrations?


Yes
Original post by NutterFrutter
Yes


hows med school going?
Original post by James A
hows med school going?


Still on gap year. :lol:

Spoiler

Original post by NutterFrutter
Still on gap year. :lol:

Spoiler



No nooo, i meant as in, have you secured your place?

Apologies for the confusion.

What have you been up to lately man?

It's hard to get hold of you because you're always on the sly :sly:.
Reply 379
Avatar for DishyBob
DishyBob
Do we need to know all the organic reactions? Like all the reactions pathways and how to get from one reactant to a product with multiple steps?:frown:

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