The Student Room Group
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>

This discussion is now closed.

Check out other Related discussions

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

Scroll to see replies

the international science edexcel papers this year is different from the one in uk! my offer requires an A in chemistry so i need to get 77% (only 83% in AS) this year... but my unit 4 was horrible, it was a difficult paper and I've lost like 5 marks by stupid mistakes, not even sure if i can get an A for that unit :frown: feel like im gonna miss my offer
Original post by lordmackery
What does everybody want/need in this paper then?


Need 96 for an A*

Posted from TSR Mobile
Original post by JRP95
Hmm I'd take a gamble and not bother then, a big steam distillation question already came up a couple of years ago so they'll probably do something on recrystallisation/reflux/fractional distillation.

Also we don't need to know about all that stuff you said after the steam distillation?

Lol there are questions on recrystallisation/reflux/fractional distillation almost every year in unit 6b, the international alternative paper
Reply 1543
Avatar for senz72
senz72
19
Original post by lordmackery
What does everybody want/need in this paper then?


I need a B in chemistry which should be achievable I hope. I need 49 UMS. Want to push for an A but it seems a bit distant due to exam stress and lack of revision. Oh what have I done...

Posted from TSR Mobile
So practice questions guys.

Explain how Chomium hydroxide complex ions are amphoteric?
Can someone please explain what is happening from CuI to F and from F to C by shaking and how to get from B to CuS04 again
Capture.JPG36.5KB
Just did my first past paper today and I found it outrageously difficult (January 2011) :/

I understood most questions after going through the mark scheme and referring back to my book, however there was a question 15iv ... which required me to know about "azo-dyes" ??!!

That made no sense to me and it was worth 5 marks... along with another 5 marker which was the final question. I didn't have a clue what section C was all about :tongue:

This unit is stupendously difficult! :frown:


Original post by DrewYouTwo
So practice questions guys.

Explain how Chomium hydroxide complex ions are amphoteric?


They can be further deprotonated to form water or they can react with H+ to form H2O ligands in the complex?
how is it oxidised when reacting with iodine??? surely its reduced ??
Capture.JPG10.9KB
Original post by Knoyle quiah
how is it oxidised when reacting with iodine??? surely its reduced ??


The sulfur in thiosfulate ion is oxidized by the iodine... one clue is that the iodine has been reduced from 0 to -1 state... therefore thiosulfate must have been oxidized! Since it's a redox reaction...

S2O3^2- .... the oxidizing state of sulfate here is:

Well oxygen -2 x 3 = -6.... there's already -2 charge.... -4 ... therefore each of two sulfur ions must be in the +2 state

then in S4O6^2- .... -2 x 6= -12 ... there's already -2 charge..... -10 .... therefore each of the 4 sulfur ions must be in the +2.5 state... and increase in oxidation number (by 0.5) means it has been oxidized :smile:
Reply 1549
Avatar for jojo1616
jojo1616
Can anyone explain this question ?thx
Posted from TSR Mobile
1371388782175.jpg15.5KB
Original post by jojo1616
Can anyone explain this question ?thx
Posted from TSR Mobile


do you have george facer book?? page 224
(edited 10 years ago)
Original post by posthumus
The sulfur in thiosfulate ion is oxidized by the iodine... one clue is that the iodine has been reduced from 0 to -1 state... therefore thiosulfate must have been oxidized! Since it's a redox reaction...

S2O3^2- .... the oxidizing state of sulfate here is:

Well oxygen -2 x 3 = -6.... there's already -2 charge.... -4 ... therefore each of two sulfur ions must be in the +2 state

then in S4O6^2- .... -2 x 6= -12 ... there's already -2 charge..... -10 .... therefore each of the 4 sulfur ions must be in the +2.5 state... and increase in oxidation number (by 0.5) means it has been oxidized :smile:


Thank you :smile: forgot about that iodine being reduced
Original post by jojo1616
Can anyone explain this question ?thx
Posted from TSR Mobile


I don't understand this completely but it needs to have 2 Cl- atoms ionically "attached" to it.... to give 2 moles of AgCl

Therefore the charge must be +2 on the complex.... but yh like Knoyle suggested, best to refer to the George Facer book :smile:
are people learning how to make Terylene, Kevlar, and nylon 6,6 from scratch including knowing the monomers??? its on the spec but do we need to know how to make from scratch?
Reply 1554
Avatar for Bord3r
Bord3r
10
Original post by jojo1616
Can anyone explain this question ?thx
Posted from TSR Mobile


Think of it in terms of ratios. In every 1 molecule of the complex there are three chlorines.
In every molecule of AgCl there is one chlorine.
However because there's double the number of moles of AgCl compared to the complex, there are two chlorines going to AgCl for every molecule of complex.
This leaves one Chlorine which must remain in the complex, thus the answer is C. :smile:
if we were asked to show how zinc hydroxide is amphoteric by equations are these correct:

(Zn(OH)2(H2O)4] + H+ --> [Zn(OH)(H2O)5]+1
[Zn(OH)2(H2O)4] + OH- --> [Zn(OH)3(H2O)3]-1 +H2O
How much of units 1,2 and 4 do we need to know for this exam?

Posted from TSR Mobile
Reply 1557
Avatar for JRP95
JRP95
2
Original post by freakynerdlol
How much of units 1,2 and 4 do we need to know for this exam?

Posted from TSR Mobile


All organic reactions are expected to be known. (so that's Like free radical elec addition even elimination)
what is steam distillation actually used for?? i understand how it works but dont know the purpose for it
Reply 1559
Avatar for JRP95
JRP95
2
Original post by Knoyle quiah
what is steam distillation actually used for?? i understand how it works but dont know the purpose for it


If the boiling temp of the mixture you're distilling is so High that it begins to decompose you pass steam into it to lower the boiling temp so it distills at a lower temp.

Related discussions

Latest

Trending

Trending

Articles for you