Unit5/unit 4 chemistry - EDEXCEL June 2012
Chemistry exam discussion - share revision tips in preparation for GCSE, A Level and other chemistry exams and discuss how they went afterwards.
-
- Reputation:
- Overlord in Training
- Location: Up norff
- Posts: 2,130
Re: Unit5/unit 4 chemistry - EDEXCEL June 2012For question 5, look at periodic table to see the columns that the transition metals lie between. Hence, they shud have more than 3 electrons in their outer subshell. So that leads to C as the jump occurs after the 4th ionisation energy.(Original post by Leonidas12)
Could someone help me with a few questions in the June 2010 paper.
I need help with 5, 23b(iii) and 24d(i)
I also don't understand why the answer to 24c doesn't accept a test for a Ketone but says you should just test for a Carbonyl group.
http://www.edexcel.com/migrationdocu...e_20100628.pdf
23bi) Add up electrode potentials till you get to the answer in the markscheme, i can't find my electrode potentials sheet so I can't do it sorry!
24d) mole ratio hydrogen:carvone is 2:1 hence two hydrogens must have been added to one carvone molecule. And if 2 hydrogens were added, two double bonds must become single bonds, leaving only 1 double bond.
24c) it won't accept test for Ketone becoz fehlings/tollens is only meant for ketones and aldehydes. So it's gna have to be 24dnph and bromine water. There reli picky about that, but in the book it does say actually say that..
Must add that I can't be 100% sure coz I'm only revising unit 4 atm, but hopefully helpedLast edited by nmudz_009; 12-06-2012 at 00:21. -
- Reputation:
- Overlord in Training
- Location: Up norff
- Posts: 2,130
Re: Unit5/unit 4 chemistry - EDEXCEL June 2012Double the h+ ions so double the conc I think. Both are fully disassociated aswell(Original post by Sykikdoc1993)
would H2SO4 and HCL of the same concentration have same PH or will it be diferent because H2SO4 is a diprotic acid ? -
- Reputation:
- Full Member
- Location: Manchester
- Posts: 135
Re: Unit5/unit 4 chemistry - EDEXCEL June 2012yup same thats what i thought . What do we need to know abt effectiveness of a buffer solution ?(Original post by nmudz_009)
Double the h+ ions so double the conc I think. Both are fully disassociated aswell -
- Reputation:
- Exalted Member
- Posts: 287
Re: Unit5/unit 4 chemistry - EDEXCEL June 2012Some people are on here revising chem 4 - join if you want too.
http://www.scriblink.com/index.jsp?a...F21598B63B4F70 -
- Reputation:
- Exalted Member
- Posts: 300
Re: Unit5/unit 4 chemistry - EDEXCEL June 2012yh that helped thanks, I tried adding the potentials up for 23bi) but wasnt sure what way to do it or w/e(Original post by nmudz_009)
For question 5, look at periodic table to see the columns that the transition metals lie between. Hence, they shud have more than 3 electrons in their outer subshell. So that leads to C as the jump occurs after the 4th ionisation energy.
23bi) Add up electrode potentials till you get to the answer in the markscheme, i can't find my electrode potentials sheet so I can't do it sorry!
24d) mole ratio hydrogen:carvone is 2:1 hence two hydrogens must have been added to one carvone molecule. And if 2 hydrogens were added, two double bonds must become single bonds, leaving only 1 double bond.
24c) it won't accept test for Ketone becoz fehlings/tollens is only meant for ketones and aldehydes. So it's gna have to be 24dnph and bromine water. There reli picky about that, but in the book it does say actually say that..
Must add that I can't be 100% sure coz I'm only revising unit 4 atm, but hopefully helped -
- Reputation:
- Exalted and Worshipped Member
- Posts: 1,104
Re: Unit5/unit 4 chemistry - EDEXCEL June 2012Hey guys quick question. Please check if im correct
In the nitration of phenylamine.. conc nitric and sulfuric acid is added which protonates -NH2 to form -NH3+ group which withdraws electrons from the ring thus deactivating it. As a result electrophilic substitution does not occur.
Let me know if its right or wrong. Thanks. -
- Reputation:
- Benevolent Member
- Location: London
- Posts: 868
Re: Unit5/unit 4 chemistry - EDEXCEL June 2012isnt that unit5?(Original post by aqua05)
Hey guys quick question. Please check if im correct
In the nitration of phenylamine.. conc nitric and sulfuric acid is added which protonates -NH2 to form -NH3+ group which withdraws electrons from the ring thus deactivating it. As a result electrophilic substitution does not occur.
Let me know if its right or wrong. Thanks. -
- Reputation:
- Full Member
- Posts: 130
Re: Unit5/unit 4 chemistry - EDEXCEL June 2012Just need to know an ester reacts with an alcohol, and the alcohol part of the ester is replaced by the alcohol reactant. It'll give you an ester with the ''new'' alcohol in it and the displaced alcohol as the product.(Original post by arnab)
guys what do we need to know about trans-esterfication? thats the only bit i am not too sure about :/
who else is starting past-paper today? there is only about 5paper
-
- Reputation:
- Exalted and Worshipped Member
- Posts: 1,104
Re: Unit5/unit 4 chemistry - EDEXCEL June 2012Yes it is. Is it correct what i have said?(Original post by arnab)
isnt that unit5? -
- Reputation:
- Exalted and Worshipped Member
- Posts: 1,104
Re: Unit5/unit 4 chemistry - EDEXCEL June 2012Yes it is. Is what i said correct??(Original post by arnab)
isnt that unit5? -
- Reputation:
- Benevolent Member
- Location: London
- Posts: 868
Re: Unit5/unit 4 chemistry - EDEXCEL June 2012I think so but i am not 100% sure as i haven't done unit5 for the last week or so.(Original post by aqua05)
Yes it is. Is it correct what i have said? -
- Reputation:
- Full Member
- Posts: 130
Re: Unit5/unit 4 chemistry - EDEXCEL June 2012Yeah, how many nmr peaks are there for low resoluition for propan-1-ol and propan-2-ol. How many peaks are there for low nmr for propanal and propanone.(Original post by verdikt)
Can anyone give some NMR examples? Im pretty weak in solving NMR questions. -
- Reputation:
- Full Member
- Posts: 130
Re: Unit5/unit 4 chemistry - EDEXCEL June 2012Also, its definetly worth knowing why nmr is prefereed to be used in pharmaceutical industry than gas chromatography.(Original post by verdikt)
Can anyone give some NMR examples? Im pretty weak in solving NMR questions. -
- Reputation:
- Full Member
- Posts: 96
Re: Unit5/unit 4 chemistry - EDEXCEL June 2012And that's because? :P(Original post by shahofiran)
Also, its definetly worth knowing why nmr is prefereed to be used in pharmaceutical industry than gas chromatography. -
- Reputation:
- Full Member
- Posts: 130
Re: Unit5/unit 4 chemistry - EDEXCEL June 20121. Less time is taken(Original post by verdikt)
And that's because? :P
2. You have a built in reference substance (TMS), whereas gas chromatography you need to prepare one.
3. Smaller volume of solvent needed.
4. Smaller mass of sample you're testing is used for nmr, whereas for GLC it's a larger mass. -
- Reputation:
- Exalted and Worshipped Member
- Posts: 1,104
Re: Unit5/unit 4 chemistry - EDEXCEL June 2012Check this trend out(Original post by verdikt)
Can anyone give some NMR examples? Im pretty weak in solving NMR questions.
http:// http://www.thestudentroom.co...d.php?t=916834 -
- Reputation:
- Banned
- Posts: 64
Re: Unit5/unit 4 chemistry - EDEXCEL June 2012Hey, can someone help me with this question please...
Explain how a buffer solution works using this system or any other of your
choice. Support your explanation with equations.
It's in the January 2010 paper, thanks in advance
