AQA CHEM4 discussion/unofficial mark scheme

Reply 220

username1133132

15

Original post by SubwayLover1

Thankyou so much!

What other mechanisms were there?? I can't remember at all!

Electrophilic sub
Nucleophillic addition

I think that was it!

Reply 221

SubwayLover1

3

Original post by haj101

Electrophilic sub
Nucleophillic addition

I think that was it!

Thank-you so much!! You have made me a lot more confident !

For some reason I remember drawing a mechanism with oxygen involved !

I wish we could see the paper!

Reply 222

LearningGeek

4

could you have CH3COOH + H2O =====> CH3COO- + H30+for the first question?

Reply 223

username1133132

15

Original post by SubwayLover1

Thank-you so much!! You have made me a lot more confident !

For some reason I remember drawing a mechanism with oxygen involved !

I wish we could see the paper!

No problem :smile:

Same :/ sad times :frown:

Reply 224

peachlet

6

salam, che joori be varaghe emtehani dastresi peyda kardi baad az inke javab ha ro post koni? motmaeni ghabool mishi? man dobare saale bad emtehan midam. kheyli shimim zaeef shode. U chi?thank you reply me back please

Reply 225

peachlet

6

chejoor inhame javab dadid?

Reply 226

SubwayLover1

3

Original post by LearningGeek

could you have CH3COOH + H2O =====> CH3COO- + H30+for the first question?

Yep

Thats correct :biggrin:

Thats better because it said how ethanoic acid reacts with water :smile:

thats 100% correct :smile:

Reply 227

Kaya22

2

The acid questions are wrong on this marksheme
who the hell wrote this?!

Reply 228

LearningGeek

4

Original post by SubwayLover1

Yep

Thats correct :biggrin:

Thats better because it said how ethanoic acid reacts with water :smile:

thats 100% correct :smile:

phew! I was getting worried for a moment, thank you :smile:

Reply 229

emilies18

1

what other Qs were there not mentioned in this ms? :smile:

thanks

Reply 230

AnnieHerbert

My answer for the following question:

Why is lidocaine hydrochloride used in medicine?

One NH2 group has been protonated in lidocaine hydrochloride, but neither group has been in lidocaine. This means the lidocaine the molecule is basic due to the two NH2 groups, but lidocaine hydrochloride is neutral, as equal amounts of H+ will dissciate from the NH3+ group as protonate the NH2 group, therefore lidocaine hydrochloride will not change the pH of blood, but lidocaine might?
Does this answer sound feasible? I have not seen many other answers to this question.

Reply 231

thehollowcrown

12

Original post by Kaya22

The acid questions are wrong on this marksheme
who the hell wrote this?!

why are they wrong? no need to be rude.

Reply 232

Haz_jt

Original post by MissVerma

CH3 O C(CH3)2 CH2CH2 OH
That's exactly what quite a few of us got!

Urgh I was so close but ran out of time I ended up scribbling down CH3OCH2CH2C(CH3)2OH I got my two CH3 groups the other way around to the two CH2's... Just thinking about it though would it matter because it still means both CH3 groups and equal and adjacent to an O as is one of the CH2's... Just the other O???

Reply 233

Medlad101

1

Original post by Kaya22

The acid questions are wrong on this marksheme
who the hell wrote this?!

they're right

Reply 234

Kaya22

2

[QUOTE="Medlad101;65816515"]they're right[/QUOTE

ohh on the new one they are, i was looking at the old one with CH3OOH2! silly me!

Reply 235

StarlightHope

1

Original post by logicmaryam

Heey guys, I think we can all agree this paper was one of the hardest CHEM4 papers ever.

Question 9 Notes
Potassium dichromate turns green, either a primary or secondary alcohol, or aldehyde
O-H absorption in the Mass spec
O-H in NMR spectrum, singlet obvs
CH3-O present in NMR spectrum, singlet
RCH2 in NMR spectrum, triplet ?
R(CH3)2 in NMR spectrum, doublet ?

Omg I got everything apart from the potassium dichromate! Maybe I didn't read the question clearly in a panic. Last 10 mins lol :colondollar:

Reply 236

SubwayLover1

3

Original post by AnnieHerbert

My answer for the following question:

Why is lidocaine hydrochloride used in medicine?

One NH2 group has been protonated in lidocaine hydrochloride, but neither group has been in lidocaine. This means the lidocaine the molecule is basic due to the two NH2 groups, but lidocaine hydrochloride is neutral, as equal amounts of H+ will dissciate from the NH3+ group as protonate the NH2 group, therefore lidocaine hydrochloride will not change the pH of blood, but lidocaine might?
Does this answer sound feasible? I have not seen many other answers to this question.

I said after its been protonated it will form an ammonium salt . Ammonium salts are ionic and can dissolve in water which means they can easily be delivered :smile:

Reply 237

username2280751

2

Knew it was LiAlH4, stupidly I said NaBH4 because I felt pressed for time, it was one of the last things I revised!

Think I've dropped ~10-15 marks being brutally honest, don't care about getting an A* I just want to get an A and enough to help boost up marks that I may have dropped on other papers!

Reply 238

username2280751

2

For last question I just put all of the structures that would be present due to the spectra, that it would be a primary/secondary alcohol and from the IR spec only no C=O/C=C bonds, then the displayed structure which was CH3OCH2CH2C(CH3)2(OH) - I really don't know what else you could have said/done for that.

Reply 239

peachlet

6

Hi , I have a question, how did you find all the answers to questions straight away after the exam date? I mean , did your college give you an extra paper and you worked out the paper at home to publish the answers online? I.e will you pass or retake it next year?

AQA CHEM4 discussion/unofficial mark scheme

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