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Edexcel A2 Chemistry Exams -6CH04 (14th June) and 6CH05 (22nd June) Discussion Thread

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This question is from the jan 2015 paper IAL:http://i.imgur.com/u8Ckk75.pngThe question is quite easy, but it is the next part which is tricky:http://i.imgur.com/KsFXyxn.pngThe answer is ethanoic acid.Can someone explain how ethanoic acid is formed? :/

Not sure if this is correct as I haven't really revised that part of the course yet but I think if you react CH3CONH2(ethanamide - D) with excess NaOH, you will get CH3COO - Na + (Solution E) which is a carboxylate ion. Then if you react the carboxylate ion with a strong acid (sulphuric acid) you will get ethanoic acid.

The fact that it releases effervescence is just confirmation that it is in fact an acid as you probs already knew. But honestly I have no clue... :\ I'm only doing it from memory and what I remember from amide hydrolysis lol

(edited 8 years ago)

Reply 21

therecovery

Original post by setarcos

They say efferverscence occurs which means it has to be an acid.In the first part, they say an organic liquid is obtained. It addition, since we are using ethanoyl chloride, we are dealing with a 2 carbon compound. Hence, it is ethanoic acid. The key here is reading the question properly.

Reply 22

therecovery

http://i.imgur.com/8Que4Q9.png

im trying to relate it to reduction potential, but im getting nowhere.
@aymanzayedmannan, any idea? :/

Reply 23

samb1234

Original post by therecovery

http://i.imgur.com/8Que4Q9.png

im trying to relate it to reduction potential, but im getting nowhere.
@aymanzayedmannan, any idea? :/

If i have two species woth reduction potentials of say 0.7v and the other as -0.2 which one will be reduced and which one will be oxidised

Reply 24

therecovery

Original post by samb1234

If i have two species woth reduction potentials of say 0.7v and the other as -0.2 which one will be reduced and which one will be oxidised

0.7v is reduced
-0.2v is oxidized

Reply 25

Ayman!

Original post by therecovery

http://i.imgur.com/8Que4Q9.png

im trying to relate it to reduction potential, but im getting nowhere.
@aymanzayedmannan, any idea? :/

You've got the right idea :borat:

Is this from U3? I had it as a mock, I think. I did it by writing out the overall reactions along with their E_cellvalues.

Reply 26

samb1234

Original post by therecovery

0.7v is reduced
-0.2v is oxidized

so how can we extend that to this question

Reply 27

therecovery

Original post by samb1234

so how can we extend that to this question

the reaction which gives the largest negative voltage will give the lowest oxidation number? :biggrin:

Original post by aymanzayedmannan

You've got the right idea :borat:

Is this from U3? I had it as a mock, I think. I did it by writing out the overall reactions along with their E_cellvalues.

Jan 2015 U6 :3
can you explain the full procedure on as to how you got it?

Reply 28

samb1234

Original post by therecovery

the reaction which gives the largest negative voltage will give the lowest oxidation number? :biggrin:

Jan 2015 U6 :3
can you explain the full procedure on as to how you got it?

What happens to the oxidation state of a reducing agent

Reply 29

therecovery

Original post by samb1234

What happens to the oxidation state of a reducing agent

it becomes more positive

Reply 30

samb1234

Original post by therecovery

it becomes more positive

i.e. it is oxidised. How can we use the same principles from the hypothetical question earlier then

Reply 31

setarcos

Original post by therecovery

Erm kinda confused, did u answer your own question there? I was trying to help lol :tongue:

Reply 32

therecovery

Original post by setarcos

Erm kinda confused, did u answer your own question there? I was trying to help lol :tongue:

i managed to answer it with the help of my teacher. thought id let you know as well so you too can learn from it :smile:

Original post by samb1234

i.e. it is oxidised. How can we use the same principles from the hypothetical question earlier then

this is going to sound a bit rude and i dont mean to be rude, but can you get to the point? :/

Reply 33

samb1234

Original post by therecovery

i managed to answer it with the help of my teacher. thought id let you know as well so you too can learn from it :smile:

this is going to sound a bit rude and i dont mean to be rude, but can you get to the point? :/

I was sort of hoping that by giving you hints you would work out how to do it, which is a much better outcome for you than me just telling you the answer. Anyway, we have established that a reducing agent in a reaction is itself oxidised, and that with 2 half equations the one with the more -ve ecell is oxidised. Therefore the reducing agent can only reduce the other species in the reaction if its ecell is lower than the ecell of the other part of the half equation

Reply 34

jmck3

I sat Unit 1 and 2 in May/June 2015 and Im sitting unit 4 and 5 this June! I'm not repeating either Unit 1 or 2 - do our marks achieved in unit 1 and 2 carry forward and count towards our whole a level mark for August 2016?

Reply 35

Funky_Giraffe

Original post by jmck3

It's like every other A-Level, so yes they will. They will contribute to your average mark over the two years (which must be over 80% to achieve at least an A)

Reply 36

Tomasio

A student carried out a titration by adding 0.032 mol dm–3 potassium hydroxidesolution to 25.0 cm3 of 0.024 mol dm–3 propanoic acid

*(ii) Explain why the pH at the equivalence point of this titration is greater than 7.

Any help would be greatly appreciated....