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

Original post by samb1234

cant zoom in on the image, what is the question

Q18 IAL paper January 2014

Reply 142

OP

Original post by ayvaak

Q18 IAL paper January 2014

We know because it reacts with fehlings it has an aldehyde group, and we also know that it must either have or be able to form something with a methyl ketone group. The oh group in A can be oxidised to a ketone (as secondary alcohol) leaving a methyl ketone group hence why can undergo iodoform

Reply 143

Original post by samb1234

We know because it reacts with fehlings it has an aldehyde group, and we also know that it must either have or be able to form something with a methyl ketone group. The oh group in A can be oxidised to a ketone (as secondary alcohol) leaving a methyl ketone group hence why can undergo iodoform

I guess what i wasn't sure on was the fact that the question insists that P ( with the OH functional group) undergoes iodoform. I didn't realise it was oxidised as a result of the reaction with I2 and NaOH. Thank you for the help

Reply 144

OP

Original post by ayvaak

I guess what i wasn't sure on was the fact that the question insists that P ( with the OH functional group) undergoes iodoform. I didn't realise it was oxidised as a result of the reaction with I2 and NaOH. Thank you for the help

there's some good info on iodoform and alcohols here http://www.chemguide.co.uk/organicprops/alcohols/iodoform.html , should give you a better idea of what is going on

Reply 145

narcotica

Just to confirm, this is for the old spec right? How did people people find the Unit 1 retake today?

Reply 146

OP

Original post by narcotica

Just to confirm, this is for the old spec right? How did people people find the Unit 1 retake today?

Yes this is old spec

Reply 147

Does anyone know if theres a IAL Jan 2016 Unit 4 and 5 paper?

Reply 148

OP

Original post by ayvaak

Does anyone know if theres a IAL Jan 2016 Unit 4 and 5 paper?

Yes there are

Reply 149

dpoojaraa

3

Original post by narcotica

Just to confirm, this is for the old spec right? How did people people find the Unit 1 retake today?

Generally, I found it good wbu?

Reply 150

Original post by samb1234

Yes there are

do you have any pdf copies that can be shared with this forum? That would be greatly appreciated :smile:

Reply 151

OP

Original post by ayvaak

do you have any pdf copies that can be shared with this forum? That would be greatly appreciated :smile:

I don't, best bet is to ask the PAMT guy if he will send it to you

Reply 152

Original post by samb1234

I don't, best bet is to ask the PAMT guy if he will send it to you

thanks. I'll try now. I'll keep you guys posted :smile:

Reply 153

tayloryeah

6

CAN SOMEONE PLEASE OUTLINE THE METHOD (from unit 4) OF CALCULATING THE PH OF SOLUTION PART WAY THROUGH A REACTION: 1. WHEN THEY ARE ARE EQUIMOLAR 2. WHEN THEY HAVE A DIFFERENT MOLE RATION
*when i refer to they i mean acid and base

Reply 154

narcotica

Original post by dpoojaraa

Generally, I found it good wbu?

I wasn't expecting some of the multiple choice questions and the first mass spectrum question about naming 2 different ions. I had 20 mins extra to check over the paper but I had to waste that time trying to guess those multiple choice questions. Did you manage to find an unofficial mark scheme btw?

(edited 7 years ago)

Reply 155

sabahshahed294

Original post by ayvaak

Does anyone know if theres a IAL Jan 2016 Unit 4 and 5 paper?

Yes, you'll find them here.
https://56leomessiphotoshop.blogspot.com/p/edexcel-january-2016-exam-materials.html

Reply 156

sabahshahed294

Original post by tayloryeah

CAN SOMEONE PLEASE OUTLINE THE METHOD (from unit 4) OF CALCULATING THE PH OF SOLUTION PART WAY THROUGH A REACTION: 1. WHEN THEY ARE ARE EQUIMOLAR 2. WHEN THEY HAVE A DIFFERENT MOLE RATION
*when i refer to they i mean acid and base

Write a balanced chemical equation between them. Once you have done that, calculate the initial moles of the reactants and products. The initial concentration for both the acid and base will be given to you. Now, once you have gotten the initial moles find out the moles that have reacted. This is done by taking the difference in their moles. Now you'll get the moles of the products. Find the new concentration using your moles of the salt and the total volume of the solution. Then if it is between let's say a carboxylic acid and a strong base such as NaOH then use the Kw value to get your hydrogen ion concentration then substitute your value of the hydrogen concentration in the formula pH= -Log[H+]. Hope this helps. :smile:

Reply 157

thebrahmabull

14

I have a few questions: halogenoalkane nucleophilic substitution with OH- 1.Why do primary halogenoalkanes follow sn2 mechanism and not sn1?

2. Why does sn1 occur in tertiary halogenoalkane and not sn2?

3. What mechanism occurs in secondary halogenoalkanes and why?

Thanks a lot. I am studying for edexcel and i couldnt find the exact info anywhere( perhaps because i didnot scan every page)

(edited 7 years ago)

Reply 158

tayloryeah

6

Original post by thebrahmabull

I have a few questions: halogenoalkane nucleophilic substitution with OH- 1.Why do primary halogenoalkanes follow sn2 mechanism and not sn1?

2. Why does sn1 occur in tertiary halogenoalkane and not sn2?

3. What mechanism occurs in secondary halogenoalkanes and why?

Thanks a lot. I am studying for edexcel and i couldnt find the exact info anywhere( perhaps because i didnot scan every page)

Firstly SN1, SN2 stands for nucleophillic substitution and the numbers refer to the number of molecules in the RDS (rate determining step)

Tertiary halogenoalkanes undergo SN1 because the halogen functional group is attached to three alkyl groups which feeds electrons to the carbonation, enabling it to be stable (more steroic hindrance)

Primary halogenoalkanes undergo SN2 because the halogen functional group is only attached to one alkyl group, so no stable carbocation forms, and as a result, the nucleophille attacks to the electron deficient area immediately. (it can form a transition state)

Secondary halogenoalkanes can go either route as there are two alkyl groups attached

:smile:

Reply 159

OP