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Edexcel Chemistry Unit 1 (23/05/2013)

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Hi, does anyone understand how to do Question 19 (e) (i) from the Jan 2013. Thank you
Apart from electrophilic addition and free radical substitution do we need to know a lot about nucleophilic substitution and other mecanisms or is it more unit 2 stuff?

Thanks in advance
Original post by marseille_h
Apart from electrophilic addition and free radical substitution do we need to know a lot about nucleophilic substitution and other mecanisms or is it more unit 2 stuff?

Thanks in advance


That's Unit 2 :smile:

Original post by maryam1996
Hi, does anyone understand how to do Question 19 (e) (i) from the Jan 2013. Thank you


Start from lowest energy level to the top energy level.
Just draw an arrow from the bottom line to the top one pointing upwards.
Ionisation of Hydrogen is high.
Original post by rainerised
what does greater effective nuclear charge mean?


Its the number of protons minus the number of core electrons.
It's the force that the outer electron 'feels' with respect to the protons in the nucleus.
I think i better go to sleep now thanks for the help Mollymod, hope the exams goes as well as bio/physics, done everything i could.

Good luck to everyone ! :smile:
What came up in Jan 2013? :smile:
Original post by Mollymod


Just learn the process, but you dont' need to know it in detail, but have a quick glance in the CGP and what each fuel can be used for. Like Kerosene and Bitumen, and what happens as you go down the fractionating column, how they're separated (ie by boiling point)


Thank you :biggrin:

I am very quickly wizzing through organic chemistry now ! :smile: And just realized that my exam is in the morning tomorrow :redface:

I have another quick question :colondollar: : For Markovnikoff's rule... could you just confirm that usually it's the "primary" over the "secondary". And unstable carbocation step gives the major product ? :smile:
Thanks for the help everyone, good luck tommorow :smile:
Original post by Mollymod
That's Unit 2 :smile:


Start from lowest energy level to the top energy level.
Just draw an arrow from the bottom line to the top one pointing upwards.
Ionisation of Hydrogen is high.


Thanks, but i just want to know what if they asked me to draw the arrow for another element's ionisation energy how will i know until which n= 1 or 2 or 3 or 4... to where i need to draw the arrow.
Reply 129
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ayat94
how many times did u guys do the past papers
i still have organic chemistry to do, so much stress but anyway good luck to every one taking this exam
can someone help me with this question please. For drivers in the UK, the legal limit of the concentration of ethanol (molar mass 46 g mol–1) in the blood is 80 mg per 100 cm3
. This is equivalent to a concentration of. thank you
Reply 132
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ayat94
convert 80 mg to grams so divide by 1000 which will give u 0.08
divide grams by Mr to get moles
to find it concentration you do moles divide by volume
ur conc should be 0.01739 or 1.739x10^-5 if you did not dived the volume by 100
Reply 133
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ayat94
round 1.73 to 1.74 mol dm-3
Original post by ayat94
convert 80 mg to grams so divide by 1000 which will give u 0.08
divide grams by Mr to get moles
to find it concentration you do moles divide by volume
ur conc should be 0.01739 or 1.739x10^-5 if you did not dived the volume by 100


thank you. can also help me with this question?
5 Ethanol (molar mass 46 g mol–1) is manufactured by the hydration of ethene (molar mass 28 g mol–1):
C2H4 + H2O o C2H5OH
In a typical process 28 tonnes of ethene produces 43.7 tonnes of ethanol. The
percentage yield of ethanol in this process is
Reply 135
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ayat94
u do divided by 46 which gives you 0.95 moles (first step just divide mass which is the tonnes by mr to get moles )
2)times moles by mr of ethene which is 28 gives you 26.6 grams this is the theratical yield
finally to find out percentage yield u do thertical dived by actual times 100
therefore 16.6 divide by 28 times 100 gives 95%
Reply 136
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ayat94
by the way for last step its is 26.6 not 16.6 divide by 28 times 100 gives 95%
Original post by ayat94
by the way for last step its is 26.6 not 16.6 divide by 28 times 100 gives 95%


thank you! you are a life saver!!!!
Original post by posthumus
Thank you :biggrin:

I am very quickly wizzing through organic chemistry now ! :smile: And just realized that my exam is in the morning tomorrow :redface:

I have another quick question :colondollar: : For Markovnikoff's rule... could you just confirm that usually it's the "primary" over the "secondary". And unstable carbocation step gives the major product ? :smile:

What do you mean? It's normally the secondary carbocation being stable over the primary carbocation, yes. As in, the hydrogen goes to the carbon with the most hydrogens which is normally the one on the 'end' of the alkyl chain. The carbons in the middle/on the second of the chain are normally saturated by another carbon and 1 hydrogen (in an alkene), whereas the one on the end normally should have two hydrogens on it, so the hydrogen would bond to that in an addition reaction and the secondary carbocation would form. It's the stable carbocation that forms the major product.

Like Hydrogen Chloride gas reacting with Propene for example will form a mixture of 1-Bromopropane and 2-Bromopropane, with 2-Bromopropane being the major product which is a secondary haloalkane; due to the stability of the secondary carbocation compared to the stability of the primary carbocation.

I realise I know too much :s-smilie:


Original post by maryam1996
Thanks, but i just want to know what if they asked me to draw the arrow for another element's ionisation energy how will i know until which n= 1 or 2 or 3 or 4... to where i need to draw the arrow.

I'll be perfectly honest and say I have no idea. I just know that hydrogen's is from the bottom to the top of that energy level diagram. I'm fairly sure it's because you're removing the outer electron from the highest energy level as hydrogen's pretty stable with it's full outer shell, so it'll be the 'highest' energy level on that diagram.

I'm sorry this reply was literally the morning of the exam.
Everyone calm down, don't freak, we will be absolutely fine :smile:
(edited 10 years ago)
Original post by Mollymod
What do you mean? It's normally the secondary carbocation being stable over the primary carbocation, yes. As in, the hydrogen goes to the carbon with the most hydrogens which is normally the one on the 'end' of the alkyl chain. The carbons in the middle/on the second of the chain are normally saturated by another carbon and 1 hydrogen (in an alkene), whereas the one on the end normally should have two hydrogens on it, so the hydrogen would bond to that in an addition reaction and the secondary carbocation would form. It's the stable carbocation that forms the major product.

Like Hydrogen Chloride gas reacting with Propene for example will form a mixture of 1-Bromopropane and 2-Bromopropane, with 2-Bromopropane being the major product which is a secondary haloalkane; due to the stability of the secondary carbocation compared to the stability of the primary carbocation.

I realise I know too much :s-smilie:



But it says in the book it will go to the one with most hydrogens attached to it :frown: In other words the carbon that is most unstable. It make sense to me for carbocation to happen on the most unstable carbon as that's the one which will probably be most reactive?? :confused:


EDIT: Woops ! It says the hydrogen atom does (in the case of HBr). Thank you Mollymod & good luck with your exam :smile: Pretty sure this is going to be a walk in the park for yourself !! :biggrin:
(edited 10 years ago)

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