No, I don't get upset anymore, I use it to my motivation :P Don't worry about it, I'm just doing Unit 4, yes. Unit 5 I'll be doing in June along with Units 4 and 5 Biology and German Units 3 and 4. :smile:

Reply 45

Yeethoven

Original post by Mollymod

No, I don't get upset anymore, I use it to my motivation :P Don't worry about it, I'm just doing Unit 4, yes. Unit 5 I'll be doing in June along with Units 4 and 5 Biology and German Units 3 and 4. :smile:

I wish I was like that lol, when people get motivated by things like that it tends to havw the oppsite effect in me. I have been procrasinating for a week now more or less. What do you think about chem. Anything tough on unit 4 you need help understanding?

Reply 46

Mollymod

15

Original post by Warlord

I wish I was like that lol, when people get motivated by things like that it tends to havw the oppsite effect in me. I have been procrasinating for a week now more or less. What do you think about chem. Anything tough on unit 4 you need help understanding?

I really love A2 Chemistry, I almost do a little bit too much of it. I'm answering a few questions on Spectroscopy at the moment, and how do you draw dimethyl ethyl propanoate? I know it's an ester but where do the methyl groups go on the ethyl bit? o.O :eek2:

It just looks like the methyl groups would make the ethyl bit the longest carbon chain which would make it a propyl group. Sorry, this is getting a bit ridiculous.

I need a bit of help with drawing carboxylic acid monomers. I guess I'll just practice that, and working out pH of a weak acid/or strong acid when half of it has been neutralised. (Question 20, part (a) (iv) on the June 2010 paper, I've attached it) , and Question 18 part (c) (ii) and (d) on June 2011's paper have me stumped as well, I've attached them to this document.

2010 JUNE UNIT 4.pdf394.7KB

2011 JUNE UNIT 4.pdf315.1KB

Reply 47

Yeethoven

Original post by Mollymod

I really love A2 Chemistry, I almost do a little bit too much of it. I'm answering a few questions on Spectroscopy at the moment, and how do you draw dimethyl ethyl propanoate? I know it's an ester but where do the methyl groups go on the ethyl bit? o.O :eek2:

It just looks like the methyl groups would make the ethyl bit the longest carbon chain which would make it a propyl group. Sorry, this is getting a bit ridiculous.

I need a bit of help with drawing carboxylic acid monomers. I guess I'll just practice that, and working out pH of a weak acid/or strong acid when half of it has been neutralised. (Question 20, part (a) (iv) on the June 2010 paper, I've attached it) , and Question 18 part (c) (ii) and (d) on June 2011's paper have me stumped as well, I've attached them to this document.

Um, I have drawn it out, I think its is ch3ch2ch2cooch(ch3)ch2(ch3). So on each of the Carbon groups after the coo ester link, add a ch3 group to each one of the 2 carbons, thus makig 1-2 di methylethyl, which is basically di methyl ethyl propanoate.

Reply 48

Mollymod

15

Perfect, that's what I initially did, but I thought it might be wrong because of the 2nd methyl group technically adding to the carbon chain and therefore suggesting it might become a propyl group.

Reply 49

Yeethoven

Original post by Mollymod

I really love A2 Chemistry, I almost do a little bit too much of it. I'm answering a few questions on Spectroscopy at the moment, and how do you draw dimethyl ethyl propanoate? I know it's an ester but where do the methyl groups go on the ethyl bit? o.O :eek2:

It just looks like the methyl groups would make the ethyl bit the longest carbon chain which would make it a propyl group. Sorry, this is getting a bit ridiculous.

I need a bit of help with drawing carboxylic acid monomers. I guess I'll just practice that, and working out pH of a weak acid/or strong acid when half of it has been neutralised. (Question 20, part (a) (iv) on the June 2010 paper, I've attached it) , and Question 18 part (c) (ii) and (d) on June 2011's paper have me stumped as well, I've attached them to this document.

I think for the half eq point, you mean where ph=pka? String acid does not do this, it is only applcable for weak acid strong base titration curves :smile:

To find it out, look at the end point volume, whereby the vertical equivalence range is, and then just half the volume from there. You will find the ph then, as at hal the volume, half of the wek acd has been neutralised, and so equas the concentration of the salt.

Sorry, I am not doing those papers yet, I will be doing them last, so when I do them, I will help you there. Skimmimg over it, I think the conc of ethanoic is half the conc of sodium hydroxide. But at end point, the moles must be equal. So essentialy, you need to work out volume needed to make the moles equal, and that will be the end point volume :smile:

Hope that helps.

Reply 50

Mollymod

15

Original post by Warlord

I think for the half eq point, you mean where ph=pka? String acid does not do this, it is only applicable for weak acid strong base titration curves :smile:

To find it out, look at the end point volume, whereby the vertical equivalence range is, and then just half the volume from there. You will find the ph then, as at hal the volume, half of the weak acid has been neutralised, and so equals the concentration of the salt.

Sorry, I am not doing those papers yet, I will be doing them last, so when I do them, I will help you there. Skimmimg over it, I think the conc of ethanoic is half the conc of sodium hydroxide. But at end point, the moles must be equal. So essentialy, you need to work out volume needed to make the moles equal, and that will be the end point volume :smile:

Hope that helps.

Thanks!

Those are some good notes :smile:

Reply 51

Yeethoven

Original post by Mollymod

Perfect, that's what I initially did, but I thought it might be wrong because of the 2nd methyl group technically adding to the carbon chain and therefore suggesting it might become a propyl group.

Dw have faith, you were right :smile:

Reply 52

Yeethoven

Original post by James A

Hi guys, thought I'd make a little thread here for the unit 5 chem exam for the upcoming January exams.

I am aware that there won't be many people on this particular thread, because this is a unit 5 paper, but let's see how this goes.

Any questions regarding this exam and pre exam discussion is all here :smile:

Whatup boy. Not sure about this, hope you know. How do you convert an amide to an amine? I thought it would be lialh4 and dry ether, two markschemes have said bromine, conc naoh, reflux? Have you come across these before? Confusing :confused:

Reply 53

NutterFrutter

Original post by Warlord

Whatup boy. Not sure about this, hope you know. How do you convert an amide to an amine? I thought it would be lialh4 and dry ether, two markschemes have said bromine, conc naoh, reflux? Have you come across these before? Confusing :confused:

This is called Hofmann's Degradation and it is near the end of the Edexcel textbook, it's just something you need to be aware of. They won't ask you to write an equation for it. (Essentially it's a way to remove a carbon atom)

Reply 54

F1's Finest

OP

21

Original post by Warlord

Whatup boy. Not sure about this, hope you know. How do you convert an amide to an amine? I thought it would be lialh4 and dry ether, two markschemes have said bromine, conc naoh, reflux? Have you come across these before? Confusing :confused:

You will need 4[H] in your equation. You only obtain the amine and water.

Reply 55

Yeethoven

Original post by NutterFrutter

This is called Hofmann's Degradation and it is near the end of the Edexcel textbook, it's just something you need to be aware of. They won't ask you to write an equation for it. (Essentially it's a way to remove a carbon atom)

Ah, I have only been using cgp, that explains it. Thanks nutter.

Reply 56

Yeethoven

Original post by James A

You will need 4[H] in your equation. You only obtain the amine and water.

Thanks.

Reply 57

d_94

7

Original post by Warlord

Not just edexcel, all the exam boards. Check on bbc, or just type in no more january exams on google.

S*** I mean, thats harsh. WTH! :angry:

Reply 58

Yeethoven

Original post by d_94

S*** I mean, thats harsh. WTH! :angry:

Not really. I had to do all my as levels and a2s in june. Although it is harder. Getting 2 chances is nicer I guess.

Reply 59

betsickles

Anyone resitting on their gap year, has your candidate number changed? My uci number is the same but my candidate number has changed? Will this effect being able to replace exams with resit results ? Hope you can help

Edexcel A2 Chemistry Unit 5 ~ 22nd January 2013

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