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# Edexcel A2 Chemistry Exams -6CH04 (14th June) and 6CH05 (22nd June) Discussion Thread watch

1. Yo peeps can someone tell me why the answer is C? I always get these half-life questions wrong and it's 1 mark I know but it's really annoying haha
2. (Original post by Don Pedro K.)
Yo peeps can someone tell me why the answer is C? I always get these half-life questions wrong and it's 1 mark I know but it's really annoying haha
In 4600 it would have had two half lives. Thus going from 1 to 0.5 to 0.25 moldm-3

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3. (Original post by Don Pedro K.)
Yo peeps can someone tell me why the answer is C? I always get these half-life questions wrong and it's 1 mark I know but it's really annoying haha
You can solve the differential equation if you get really stuck lol
4. (Original post by samb1234)
You can solve the differential equation if you get really stuck lol
Lol yeah maybe not for one mark

(Original post by ayvaak)
In 4600 it would have had two half lives. Thus going from 1 to 0.5 to 0.25 moldm-3

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AHhhhh okay I get it So after the first 2300s, the conc has halved from 1.0 to 0.50, and then in the second one it has halved from 0.5 to 0.25!!
5. (Original post by Don Pedro K.)
Lol yeah maybe not for one mark

AHhhhh okay I get it So after the first 2300s, the conc has halved from 1.0 to 0.50, and then in the second one it has halved from 0.5 to 0.25!!
Hence the if you get really stuck. If you can't remember the relationship or whatever in the exam then its relatively easy to get to it through that root, although obviously preferable not to have to do that
6. For the equation circled were we supposed to know this already or derive it ? The question is from jan 2015 q23cii)
Attached Images

7. And for this Q how do you know for sure the answer is D?
8. (Original post by ayvaak)
And for this Q how do you know for sure the answer is D?
If you learn the colours in the table on 90 of the CGP you should be able to answer that.
9. (Original post by Don Pedro K.)
If you learn the colours in the table on 90 of the CGP you should be able to answer that.
I think he/she knows the colours because he's written them next to the answers but the colours contradict the question if you get what I'm saying. Cr3+ which is the right answer according to the mark scheme should give a purple solution in excess ammonia, not a green solution. I'm also confused why the answer is D
10. (Original post by Funky_Giraffe)
I think he/she knows the colours because he's written them next to the answers but the colours contradict the question if you get what I'm saying. Cr3+ which is the right answer according to the mark scheme should give a purple solution in excess ammonia, not a green solution. I'm also confused why the answer is D
Not according to the user guide or other sources. Cr 3+ is almost always green unless it is in water solely but the way it's made means it is normally still green rather than violet
11. (Original post by samb1234)
Not according to the user guide or other sources. Cr 3+ is almost always green unless it is in water solely but the way it's made means it is normally still green rather than violet
Ah ok. Sorry for the confusion. CGP does actually state that chromium in an ammine complex is violet which is probably the source of the confusion.
12. (Original post by Funky_Giraffe)
Ah ok. Sorry for the confusion. CGP does actually state that chromium in an ammine complex is violet which is probably the source of the confusion.
Yeah that is weird. For these kind of things its probably best to go by the user guide since thats the official edexcel version, even if it may be wrong
13. (Original post by Funky_Giraffe)
I think he/she knows the colours because he's written them next to the answers but the colours contradict the question if you get what I'm saying. Cr3+ which is the right answer according to the mark scheme should give a purple solution in excess ammonia, not a green solution. I'm also confused why the answer is D
Isn't it to do with ligand substitution with Cl-/SO42- ions in water which causes the green complex colour?
14. Hi. Would someone help out in question no 18(b ii ) and c(ii) from this paper? Thanks in Advance.

https://c838cff4741acb48ae1ed62e5992...0Chemistry.pdf
15. (Original post by sabahshahed294)
Hi. Would someone help out in question no 18(b ii ) and c(ii) from this paper? Thanks in Advance.

https://c838cff4741acb48ae1ed62e5992...0Chemistry.pdf
Does it help if I tell you that ethanedioic acid is di-protic?
16. (Original post by Ayman!)
Does it help if I tell you that ethanedioic acid is di-protic?
Have you done January 2015 (IAL) unit 4? If so, how did you do ?
17. (Original post by Don Pedro K.)
Have you done January 2015 (IAL) unit 4? If so, how did you do ?
I'll do it tonight! I've just done IAL June 2014. I definitely think that the UK papers are harder than the IALs for chemistry (at least U4). I got 81/90 on June 14 which is just a mark above the A*, so cutting it close.
18. (Original post by Ayman!)
I'll do it tonight! I've just done IAL June 2014. I definitely think that the UK papers are harder than the IALs for chemistry (at least U4). I got 81/90 on June 14 which is just a mark above the A*, so cutting it close.
Danhhh nice haha! I heard the U5 IAL papers are crazy though o.O
19. (Original post by Don Pedro K.)
Have you done January 2015 (IAL) unit 4? If so, how did you do ?
Well i was gonna do a paper now anyway so ill have a look at it
20. (Original post by samb1234)
Well i was gonna do a paper now anyway so ill have a look at it
ah okay gl

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