OCR B Salter's Chemistry by Design F335 - 15th June 2015 Watch

Shantellea
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(Original post by FudgeMonkey97)
From experience (Or by talking about lowest grade boundaries) What would you consider the hardest F335 paper? Going to test myself
In June 2013 you needed 90 to get an A which is the highest I've seen


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FudgeMonkey97
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(Original post by MrPolish)
Is the value of Kw always 1x10^-14 ? Whilst working out strong bases ?
Only at room temperature I believe but the value is always given to you whether its room temperature or not
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FudgeMonkey97
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(Original post by Shantellea)
In June 2013 you needed 90 to get an A which is the highest I've seen


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Thank you, lucky me just did that paper, guess I'll close my eyes and click at random for the next one I try
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radhikagulati
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For NMR do you just talk about what the ppm value relates to and splitting? What else can you talk about?
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greencat55
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(Original post by FudgeMonkey97)
From experience (Or by talking about lowest grade boundaries) What would you consider the hardest F335 paper? Going to test myself
From what I've heard, last years was the hardest but I'm not sure. It's certainly not an easy one, its only 82/120 for an A (68.3%)! :P
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suyoof123
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June 2014,

1c-

after you do Kc *(H2)(CO2) , how do you work from there..I dont get how they figured out the rest
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greencat55
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Sorry to ask again, but I'm stumped again. :/
Does anyone know how to get the answer to (ii). The mark scheme said it is 2.73.
Part (i) is right and please ignore my scribbles :P
Thank you!!

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greencat55
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(Original post by suyoof123)
June 2014,

1c-

after you do Kc *(H2)(CO2) , how do you work from there..I dont get how they figured out the rest
You square root kc x [H2][CO2] (2.68x10^-12), to get 1.64x10^-6. That is the answer to both.

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Priya265
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Hi guys, just wondering if you could help me with a q?
http://www.ocr.org.uk/Images/175449-...-by-design.pdf
Q 3 d ii
I cant figure out why its a 3:1 ratio instead of 2:1
Mark scheme: http://www.ocr.org.uk/Images/176061-...esign-june.pdf
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jonesy123
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#150
(Original post by greencat55)
Sorry to ask again, but I'm stumped again. :/
Does anyone know how to get the answer to (ii). The mark scheme said it is 2.73.
Part (i) is right and please ignore my scribbles :P
Thank you!!

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You have volumes and concentration from part i. Multiply them up to get concentrations for A- and HA then divide Ka by A-/HA
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jonesy123
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(Original post by greencat55)
Sorry to ask again, but I'm stumped again. :/
Does anyone know how to get the answer to (ii). The mark scheme said it is 2.73.
Part (i) is right and please ignore my scribbles :P
Thank you!!

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Then -log the number you get which is the H+ concentration.
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suyoof123
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(Original post by greencat55)
You square root kc x [H2][CO2] (2.68x10^-12), to get 1.64x10^-6. That is the answer to both.

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Thank you.
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BrokenS0ulz
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(Original post by jonesy123)
You have volumes and concentration from part i. Multiply them up to get concentrations for A- and HA then divide Ka by A-/HA
What do you mean by multiply up to get concentration?

I've got a question if anyone could help: are these ways of drawing the bonds the same?Name:  ms1.png
Views: 199
Size:  7.4 KBexam board seem to use 1st way, but I've always been taught the 2nd way :s.
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FudgeMonkey97
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I've been taught that way as well, I wouldn't worry to much about it, mark schemes are hard to figure out. My chemistry teacher used to be an examiner for OCR so if he teaches the 2nd way it's bound to be accepted
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FudgeMonkey97
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#155
(Original post by greencat55)
From what I've heard, last years was the hardest but I'm not sure. It's certainly not an easy one, its only 82/120 for an A (68.3%)! :P
Thank you! Starting it now! 😏
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sunshine12321
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Hi, can anyone help with Jan 2011, question 5f part ii and iii please. I haven't got a clue how they got the answer they did. It's about equilibrium constants and shiz.

Thanks x
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suyoof123
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Is there any worth doing pre 2009 papers...the spec of this is messed seeing what came up in f334.

I feel as if i should revise for my bio,buss exams on wednesday..
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jonesy123
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(Original post by BrokenS0ulz)
What do you mean by multiply up to get concentration?

I've got a question if anyone could help: are these ways of drawing the bonds the same?Name:  ms1.png
Views: 199
Size:  7.4 KBexam board seem to use 1st way, but I've always been taught the 2nd way :s.
Just realised you already have concentration so just use those in the equation for Ka instead of salt/acid. Then divide Ka by salt/acid to get H+ concentration then -log of H+.
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Millie0118
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Hopefully it'll be nicer than our f334 paper
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docdoc02
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(Original post by BrokenS0ulz)
What do you mean by multiply up to get concentration?

I've got a question if anyone could help: are these ways of drawing the bonds the same?Name:  ms1.png
Views: 199
Size:  7.4 KBexam board seem to use 1st way, but I've always been taught the 2nd way :s.
It doesnt matter what way you do it as long as you show that they are in different planes
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