[DH3498]

Not of a weak base I don't think. Like you said on the spec it just says weak acid using Ka, strong acid using [H+] = [HA] and base using the ionic product of water

[clownfish]

(Original post by DH3498)
Not of a weak base I don't think. Like you said on the spec it just says weak acid using Ka, strong acid using [H+] = [HA] and base using the ionic product of water

This is right

[lagoom]

(Original post by moh.alt)
June 2011 F325

hi, was wondering if there's a jan 2010 past paper for this exam, it's not on the ocr website and was just wondering if the paper wasn't in the sylabus back then
thanks

[Oromis263]

(Original post by lagoom)
hi, was wondering if there's a jan 2010 past paper for this exam, it's not on the ocr website and was just wondering if the paper wasn't in the sylabus back then
thanks

Don't think there will have been a Jan 2010 paper, as the first year to sit it would have been the 2010 year, so would only have June 2010. Use previous specification papers (unifying concepts, how far how fast, etc) for extended revision.

[flowerpower1410]

thanks

also, we dont need to know about alkaline buffer solutions (eg: nh3 and nh4cl etc.) do we? just want to check

[flowerpower1410]

hey sorry another question...
can anyone explain why a more disordered system is energetically more stable?

[lagoom]

(Original post by Oromis263)
Don't think there will have been a Jan 2010 paper, as the first year to sit it would have been the 2010 year, so would only have June 2010. Use previous specification papers (unifying concepts, how far how fast, etc) for extended revision.

alright thanks, i already use unifying concepts and trasition elements, but is how far how fast really relavant?

[clownfish]

(Original post by lagoom)
alright thanks, i already use unifying concepts and trasition elements, but is how far how fast really relavant?

HFHF is really preparation for F322 - except for the part about acids, which is actually too basic for F325 anyway.

Trends & Patterns is really useful for Born Haber Cycles and it often has qs on transition elements, SEPs and redox titrations so is worth a look.

[VQG]

Subbed.

[S_Azizi]

Was just wondering in the OCR exams, for biology/chemistry is it possible to lose marks on questions if you mention wrong points despite mentioning all the correct points?

For example, a ordinary 3 marker - You mention all correct three points but then mention an extra point that may not correct. Would I be penalised for this and get 2/3 instead of 3/3? I ask this question because, I notice myself losing marks on questions whenever I add too many points, and feel like I may have added something which may not have been accurate.

I know that if it asks for three points, you are only allowed to give three points, but this is for general questions.

Also, is there some sort of way of contacting OCR as I have a few other questions about the specification, specifically about the 'synoptic questions' and the 'how science works' questions.

[SpringNicht]

How much do we need to know about the transition metal ion colours? Do we need to know all of them, or certain ones or what? :/

[SpringNicht]

(Original post by S_Azizi)
Was just wondering in the OCR exams, for biology/chemistry is it possible to lose marks on questions if you mention wrong points despite mentioning all the correct points?

For example, a ordinary 3 marker - You mention all correct three points but then mention an extra point that may not correct. Would I be penalised for this and get 2/3 instead of 3/3? I ask this question because, I notice myself losing marks on questions whenever I add too many points, and feel like I may have added something which may not have been accurate.

I know that if it asks for three points, you are only allowed to give three points, but this is for general questions.

Also, is there some sort of way of contacting OCR as I have a few other questions about the specification, specifically about the 'synoptic questions' and the 'how science works' questions.

On other exam boards marks are only knocked off if you directly contradict something you previously said that received a mark eg. Saying transition metal ions form complexes getting you a mark then saying further on everything but transition metals form complexes would get the mark knocked off.

I hope OCR isn't different...

[Oromis263]

(Original post by SpringNicht)
How much do we need to know about the transition metal ion colours? Do we need to know all of them, or certain ones or what? :/

Not sure, but Iron II, my teacher just said "two peas in a pod". Peas are green, Iron II is green. >.< That being said, I've not forgotten it ^_^

[S_Azizi]

(Original post by SpringNicht)
On other exam boards marks are only knocked off if you directly contradict something you previously said that received a mark eg. Saying transition metal ions form complexes getting you a mark then saying further on everything but transition metals form complexes would get the mark knocked off.

I hope OCR isn't different...

Ok

Thanks for the help.

[pcorbett94]

(Original post by SpringNicht)
How much do we need to know about the transition metal ion colours? Do we need to know all of them, or certain ones or what? :/

My teacher is having us remember the following:

Iron (II) ions - Green
Iron (III) ions - Yellow
Copper (II) ions - Blue
Cobalt (II) ions - Pink

Iron (II) Hydroxide - Green precipitate (turns reddish brown on standing)
Iron (III) Hydroxide - Reddish precipitate
Copper (II) Hydroxide - Blue Precipitate
Cobalt (II) Hydroxide - Blue Precipitate

[Cu(H₂O)₆]²⁺ ---> [CuCl₄]^2-
Blue ---> Green

[Co(H₂O)₆]²⁺ ---> [CoCl₄]^2-
Pink ---> Blue

I'm hoping that these are the only ones we need to know because I'm too lazy to remember colour changes.

[--NWzD9--]

on q.2a) of june 2010 paper, mark scheme says:



Why is this not also correct?

[pcorbett94]

(Original post by --NWzD9--)
on q.2a) of june 2010 paper, mark scheme says:



Why is this not also correct?

The charges don't balance. The overall charge of the left hand side is +2 (+6-3-1). The overall charge of the right hand side is 0. The overall charges must always be the same on each side.

[clownfish]

(Original post by pcorbett94)
My teacher is having us remember the following:

Iron (II) ions - Green
Iron (III) ions - Yellow
Copper (II) ions - Blue
Cobalt (II) ions - Pink

Iron (II) Hydroxide - Green precipitate (turns reddish brown on standing)
Iron (III) Hydroxide - Reddish precipitate
Copper (II) Hydroxide - Blue Precipitate
Cobalt (II) Hydroxide - Blue Precipitate

[Cu(H₂O)₆]²⁺ ---> [CuCl₄]^2-
Blue ---> Green

[Co(H₂O)₆]²⁺ ---> [CoCl₄]^2-
Pink ---> Blue

I'm hoping that these are the only ones we need to know because I'm too lazy to remember colour changes.

The only one you are missing is:
[Cu(H₂O)₆]²⁺ ---> [Cu(H₂O)₂(NH₃)₄]²⁺
blue --> deep blue

[Cath-ay]

(Original post by pcorbett94)
My teacher is having us remember the following:

Iron (II) ions - Green
Iron (III) ions - Yellow
Copper (II) ions - Blue
Cobalt (II) ions - Pink

Iron (II) Hydroxide - Green precipitate (turns reddish brown on standing)
Iron (III) Hydroxide - Reddish precipitate
Copper (II) Hydroxide - Blue Precipitate
Cobalt (II) Hydroxide - Blue Precipitate

[Cu(H₂O)₆]²⁺ ---> [CuCl₄]^2-
Blue ---> Green

[Co(H₂O)₆]²⁺ ---> [CoCl₄]^2-
Pink ---> Blue

I'm hoping that these are the only ones we need to know because I'm too lazy to remember colour changes.

Correct me if I'm wrong but for [Cu(H 2 O) 6] 2+ ---> [CuCl 4]
2-
Isn't the colour change Blue ---> (Green--->) Yellow when you add Cl- ions to excess? :/

[clownfish]

(Original post by Cath-ay)
Correct me if I'm wrong but for [Cu(H 2 O) 6] 2+ ---> [CuCl 4]
2-
Isn't the colour change Blue ---> (Green--->) Yellow when you add Cl- ions to excess? :/

This is correct