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Edexcel - Chemistry Unit 2 - 4 June 2013

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the question about X was the most molecules with this energy. the one with carbon neutrality i got really confused but finally i chose the energy released by burning one ton of biofuel and i hopr this is right because carbon neutr4ality is concerned with carbon dioxide absorbed or released not with energy.
Guys feel free to say what you got? i am not 100% sure that i have got all mcqs right. Rest of them were okay i didnt need to th9ink alot about them but one mcq i think i got wrong is the one fullerene one. i chose option that fullerene exist as small molecules while graphite and diamond have got giant structures. any other mcq someone wants to remind me of?
and the question about SN1 and SN2 mechanism there was one question in past paper i dont know exactly which paper but it said that secondary halogenoalkanes go by SN1. for colour change i am not sure but i wrote since there was no indicator and there was just iodine in water which originally had brown colour so by addition of thiosulphate the colour becomes very pale brown in end. i dont think so i got this one right. the question about hydrolysis i wrote that acids generate proton hydrogen ion in water so by adding HCL more H+ ions will be produced. the equilibrium will be disturbed and therefore reaction moves to left producing more water and bromine.
Original post by jollygood
and the question about SN1 and SN2 mechanism there was one question in past paper i dont know exactly which paper but it said that secondary halogenoalkanes go by SN1. for colour change i am not sure but i wrote since there was no indicator and there was just iodine in water which originally had brown colour so by addition of thiosulphate the colour becomes very pale brown in end. i dont think so i got this one right. the question about hydrolysis i wrote that acids generate proton hydrogen ion in water so by adding HCL more H+ ions will be produced. the equilibrium will be disturbed and therefore reaction moves to left producing more water and bromine.


Are you sure about the SN1 mechanism bit? I'm pretty sure they'll accept both, there's no set rule for it
Original post by jollygood
Guys feel free to say what you got? i am not 100% sure that i have got all mcqs right. Rest of them were okay i didnt need to th9ink alot about them but one mcq i think i got wrong is the one fullerene one. i chose option that fullerene exist as small molecules while graphite and diamond have got giant structures. any other mcq someone wants to remind me of?


Thats correct, isnt it?
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Original post by jollygood
Okay guys so i think the paper was harder than previous ones specially the MCQS. But i hope i didnt lose more than 6-7 marks maximum. starting with mcqs i wrote SF6 , CCl4, 2-chlorobutane. for increasing covalent characer i said NaCl, MgCl2 to SiCl4. then for sodium chloride solubility i chose the hydration enthalpy one that was most appropriate.


Increasing covalent character was down group 1 I think


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Original post by Goods
Increasing covalent character was down group 1 I think


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Yeah, I guessed that one. The option that included Rb?

I was so close to choosing the last option which had the halides. Doesn't an increase in covalent character refer to how strongly an atom can pull a pair of electons? Does that refer to covalency?? :s-smilie:
Increasing covalent character is NOT down group 1. I could get egg in my face here for sounding so confident :s-smilie: BUT doesnt covalency relate to polarising power and distorted ionic bonds, so going down the group polarising power decreases and it becomes less covalent.
Original post by James A
Yeah, I guessed that one. The option that included Rb?

I was so close to choosing the last option which had the halides. Doesn't an increase in covalent character refer to how strongly an atom can pull a pair of electons? Does that refer to covalency?? :s-smilie:


what in thought was that the most easily an ionic bond is formed is when the metal has really low ionisation energy and non metal has high electron affinity. the non metal was same so in case of metals the ionisation energy kept on increasing across a period so harder to bond ionically. and one more thing u guys know we show bonding of aluminium chloride sometimes as ionic sometimes covalent and after that silicon chloride is purely covalent so thats why i chose that?
Original post by GCSE-help
Increasing covalent character is NOT down group 1. I could get egg in my face here for sounding so confident :s-smilie: BUT doesnt covalency relate to polarising power and distorted ionic bonds, so going down the group polarising power decreases and it becomes less covalent.


So was it the option that involved the halides? (F, Cl, Br) ?
Original post by James A
So was it the option that involved the halides? (F, Cl, Br) ?


Yes I think so, because the halides get bigger so they can be more easily polarised, as bigger anions are easier to polarise. It was a tricky question.

And to be honest, I don't remember what I put, but I think your point about the going down group 1 argument is wrong. I may be wrong though :colondollar:
Original post by GCSE-help
Increasing covalent character is NOT down group 1. I could get egg in my face here for sounding so confident :s-smilie: BUT doesnt covalency relate to polarising power and distorted ionic bonds, so going down the group polarising power decreases and it becomes less covalent.


thats exactly right the polarising power decreases down group, so cation will not be able to distort the electron cloud..
Original post by geor
I think I put ethanal or propanal (can't quite remember) for that one


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I put propanal too. 29: CH3CH2
57: CH3CH2CO
58: CH3CH2CHO
I hated this exam! It seemed like there were too many "let's test your memory" questions (i.e reactions&products etc) and no enough "let's test your actual understanding" questions (explaining mechanisms ect)?
Would you all agree? Also, any thoughts on grade boundaries?
Original post by Kurraiyo
I put propanal too. 29: CH3CH2
57: CH3CH2CO
58: CH3CH2CHO


was it 29 nor 43?
Original post by geor
I completely agree. I knew the chemistry inside out but I tripped up because I over complicated easy questions and was unsure on stupid questions like freaking tests!


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Exactly!! I understand all of the chemistry and WHY everything happpens.. But just because my memory's not good enough to remember every single alcohol and halo reaction I'm not gonna get a good grade for that!
I'm sorry, but I thought I was sitting a chemistry test not a memory test!
Original post by jollygood
then for the mass spectrum with 43,57,58 i chose propanone. i chose ozone sepletion for last one. volume calculation was the first option if i am not wrong


I put down the aldehyde. The first option I think.
Original post by geor
Haha, yes. The other past papers were much more on the true chemistry. This paper was just awful, I'm hoping the grade boundaries go down from january


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They better do! Otherwise I can kiss goodbye to my A :frown:
Original post by geor
I agree with you except I'm not sure about the sodium chloride one. Why would energy being released from the hydration of ions mean it would be more soluble in water? Energy would be released if they were attracted to hexane molecules as well just not as much - but that option didnt specify that.
To be honest I didn't like any of the choices....


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Energy released from the hydration is what compensates for the energy lost from the bond breaking. Its in the george facer book.
Original post by James A
I don't think they would accept the reaction with water or chlorine.

When they referred to don't heat, they meant don't carry out thermal decomposition on it.

Flame test is the best way to distinguish between the two samples.


Ok thank you

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