OCR B F335 - Chemistry by Design - 13th June 2012
Chemistry exam discussion - share revision tips in preparation for GCSE, A Level and other chemistry exams and discuss how they went afterwards.
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Re: OCR B F335 - Chemistry by Design - 13th June 2012Okay, so Q4 ai) First you need the formula for the combustion of benzene. Benzene is C6H6(Original post by Princess Kawaii)
Okay I did my first paper for this topic today and got on the dot B
not good when I need an A.
I did f335 June 10 paper and found some questions difficult ...can anyone explain how you would work them out ... I've look at the mark scheme but they don't always lay the answer/working out in steps.
some of the questions are:
- Q4 a(i)
- Q5 e(v)
- Q5 f
Here's the paper: http://pdf.ocr.org.uk/download/pp_10..._gce_f335.pdf?
Thanks alot
soo.. C6H6 + 9O2 -> 6CO2 + 6H2O Just double check this, I only did it quickly
Now we need to work out what that 1.00g of benzene is in mol. So mass= mol x Mr
So 1.00/[6x12+6]
= 1/78 [Haven't rounded cause I've not finished with that number yet]
For every benzene you get 6 CO2 's
So 6x [1/78] = 6/78 mol of CO2
You want the mass so, 6/78 x [12+16x2] = 44/13 = 3.38 g [3sf]
However, it's only a two marker, and it mentions empirical formula so there must be a quicker way using that? Cause I've explained it though it looks longer, so it might be okay doing it that way. I would.
Q5 ev) pH = -log[H+]
Because I haven't done the rest of the question I'm not sure what the value of [H+] is, though I'm sure the first parts lead you towards it. Use one of the equations for Ka or something
I'm also not sure about part f, sorry :/ need to think about it, it might be one that I was given to do, so if no-one else answers maybe I'll do it tomorrow
Hope I helped on q4 though, and I did check that answer
Happy Chemistry[ing]!Last edited by Tantail; 25-05-2012 at 18:16. Reason: Sorry didn't see that you'd looked at the markscheme already >.< -
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Re: OCR B F335 - Chemistry by Design - 13th June 2012Just been revision water and enthalpy dissolving and stuff. Not too hard, but it can be confusing.
Ionic substances will not dissolve in non-polar solvent
Covalent substances with never dissolve in polar solvents.
And ionic substances will usually dissolve in polar substance due the attraction of the hydrogen on water to the negative ions and the oxygen on water attracted to positive ions. -
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Re: OCR B F335 - Chemistry by Design - 13th June 2012No we don't.(Original post by Einy)
Do we need to know about Kp for equilibrium constants? Its not in chemical ideas - but its in the revision guide CGP and it appears the specimin paper? What do you guys think? They took it out this year. It still appears int he spec paper because that was written at the begining of the new specification in sept09. Hope that clears it all.
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Re: OCR B F335 - Chemistry by Design - 13th June 2012(Original post by master_blaster66)
isit just me or RE THERE THINGS IN F335 WHICH YOU JUST HAVE TO GUESS SOMETIMES :/
Sometimes questions pop up on stuff we 'haven't' done. Usually they're only a few marks, my teacher says they're to distinguish the A* from the A students. Don't worry about them, do all the other questions and come back if you have time. They're normally the sort of question you can work out, from what they give you, just read the question carefully. For example it may mention copper [II] something, telling you copper has a plus 2 oxidation state in the compound. They won't put anything in that we can't work out, you just have to understand the chemistry, not just do it, it'll make it alot easier. Unlike maths where you just need to know the routine.
Sorry about the lengthy text, hope that is helpful
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Re: OCR B F335 - Chemistry by Design - 13th June 2012You know for example when it says Copper (II), I understand it has a 2+ charge but how do u know whether whatever is in the brackets is negative or positive? will it always be + ??(Original post by Tantail)
Sometimes questions pop up on stuff we 'haven't' done. Usually they're only a few marks, my teacher says they're to distinguish the A* from the A students. Don't worry about them, do all the other questions and come back if you have time. They're normally the sort of question you can work out, from what they give you, just read the question carefully. For example it may mention copper [II] something, telling you copper has a plus 2 oxidation state in the compound. They won't put anything in that we can't work out, you just have to understand the chemistry, not just do it, it'll make it alot easier. Unlike maths where you just need to know the routine.
Sorry about the lengthy text, hope that is helpful
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Re: OCR B F335 - Chemistry by Design - 13th June 2012Usually it's positive, I think. I've never come across a negative one.(Original post by Bi0logical)
You know for example when it says Copper (II), I understand it has a 2+ charge but how do u know whether whatever is in the brackets is negative or positive? will it always be + ?? -
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Re: OCR B F335 - Chemistry by Design - 13th June 2012(Original post by Bi0logical)
You know for example when it says Copper (II), I understand it has a 2+ charge but how do u know whether whatever is in the brackets is negative or positive? will it always be + ??
Same. Unless it's specified, I think it's just supposed to be assumed it's positive for Cu (II).(Original post by navarre)
Usually it's positive, I think. I've never come across a negative one. -
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Re: OCR B F335 - Chemistry by Design - 13th June 2012Metals have a much greater tendency to form positive ions, you like never see negative metal ions, so assume its positive.(Original post by SimpleGirl)
Same. Unless it's specified, I think it's just supposed to be assumed it's positive for Cu (II). -
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Re: OCR B F335 - Chemistry by Design - 13th June 2012http://www.thestudentroom.co.uk/show....php?t=1999876
i found the markscheeme -
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Wasnt too bad, a little bit of the synoptic stuff got me.(Original post by Beffnaay)
What did everyone think of the January 2012 paper? Hard or easy? -
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Re: OCR B F335 - Chemistry by Design - 13th June 2012you always say that every exam season, and always come out with 90% +(Original post by LexxieK)
Really not ready for this
What do I need to know for storylines?!
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Seriously I've done nothing, urgh. I got an offer which doesn't require chemistry A2 but now I feel bad for doing nothing and know I must!(Original post by master_blaster66)
you always say that every exam season, and always come out with 90% +
This was posted from The Student Room's iPhone/iPad App
not good when I need an A.
