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Edexcel IAL, Unit 5: Transition Metals and Organic Nitrogen Chemistry. 22-Jun-2016

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Reply 60
Original post by Tomasio
I have finished revising the content but have virtually done no question practice whatsoever, even throughout the entire year I did barely in question answering homeworks...... Is it too late for me to get up to a good grade??


Not really. start doing the past papers today and you'll be fine.. Check 'em yourself and read examiner reports!
Reply 61
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.

Unit 4, but still, Anyone care to help? did a past paper and this was the only question that stumped me.
(edited 7 years ago)
Reply 62
Original post by 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.

Unit 4, but still, Anyone care to help? did a past paper and this was the only question that stumped me.


I think it's coz the KOH is a strong base but propanoic acid is a weak acid
plus the concentration of KOH is also higher
Reply 63
Original post by 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.

Unit 4, but still, Anyone care to help? did a past paper and this was the only question that stumped me.


Yeah, 'coz KOH is a strong base and dissociates completely whereas propanoic acid doesn't dissociate completely, so lesser H+ than OH- if same conentration was added. Anyway so, the PH would be greater 'coz when a weak acid and strong base neutralize the equivalence point is in alkaline range and in acidic range if strong acid for eg. HCl neutralizes weak base for eg. NH3. It's only 7 if both are strong! for eg. HCl and KOH.
its because the propanoic acid's conjugate base is proton deficient. therefore it reacts with the water that is present in the aqueous solution and forms oh- ions, therefore increasing the concentration of oh- in solution, making the ph above 7. its to do with the auto ionisation of water and such but I'm pretty sure thats right. saying its strong base and weak acid isn't sufficient to get more than 1 mark, however i may be over complicating the answer if the question is only worth 1 mark
Reply 65
Original post by thymolphthalein
Good luck. :biggrin:

Make sure to do a quick review of Organic Chemistry from all the units and Redox Equilbria. It might seem like a lot (the joy of synoptic exams), but Unit 5 will definitely be easier with a clear comprehension of earlier units, especially the highly relevant ones. :h:


Unit 5 is the toughest of all A2 exams :/
Reply 66
Original post by Aimen.
Unit 5 is the toughest of all A2 exams :/


It's a close call between C4 and U5.
Reply 67
Original post by Mehodax
It's a close call between C4 and U5.


I don't take maths but my classmates say it's pretty easy. but probably cuz our maths teacher is so cool!
Reply 68
Subbing :3
Reply 69
Original post by Aimen.
I don't take maths but my classmates say it's pretty easy. but probably cuz our maths teacher is so cool!


Trust me, you have no idea till you do it on your own!
yo guys i cant find any unit 2 thread for 2016, could someone help me w this one question though? Q1b - the answers A but i thought D made more sense?
https://e91d34a60c48d35030cf61ddda06cffc30feeddf.googledrive.com/host/0B1ZiqBksUHNYaklpczRpVjg4ZjA/June%202014%20(IAL)%20QP%20-%20Unit%202%20Edexcel%20Chemistry.pdf
Reply 71
anyone know where any extra unit 5 questions might be found?
I have now done most of the past papers.
Reply 72
Does anyone know an active thread to unit 6 IAL chem?
Volume is smaller, so colour intensity of all gases increase
Original post by imnoteinstein
yo guys i cant find any unit 2 thread for 2016, could someone help me w this one question though? Q1b - the answers A but i thought D made more sense?
https://e91d34a60c48d35030cf61ddda06cffc30feeddf.googledrive.com/host/0B1ZiqBksUHNYaklpczRpVjg4ZjA/June%202014%20(IAL)%20QP%20-%20Unit%202%20Edexcel%20Chemistry.pdf
Reply 74
I just made a thread for chem unit 6, it's actually awkward asking but could we guys discuss that in there.. cuz I couldn't find one~!

http://www.thestudentroom.co.uk/showthread.php?t=4079863
Original post by ambrose.6629
Volume is smaller, so colour intensity of all gases increase


righttttt thanks alot!
To measure the standard electrode potential for the Ag+(aq)|Ag(s) electrode, the mostsuitable chemical for the solution in a salt bridge to connect the two half cells is:
A potassium chloride.
B potassium iodide.
C potassium nitrate.
D potassium sulfate.

answers C but why?
https://a5c076379da85d2c0b501a60f1a40f8eeaf5f812.googledrive.com/host/0B1ZiqBksUHNYdEFJbUVsVUl3Ums/June%202012%20QP%20-%20Unit%205%20Edexcel%20Chemistry.pdf

Q6, why doesnt DNPH react with it, it has a C=O group :O and how do we tell it reacts with NaOH and HCl?
Reply 78
Original post by imnoteinstein
To measure the standard electrode potential for the Ag+(aq)|Ag(s) electrode, the mostsuitable chemical for the solution in a salt bridge to connect the two half cells is:
A potassium chloride.
B potassium iodide.
C potassium nitrate.
D potassium sulfate.

answers C but why?

I think it's because K+ as seen for all options is a very inert cation (had noble gas configuration)
and most inert anion is NO3-
Reply 79
Original post by imnoteinstein
https://a5c076379da85d2c0b501a60f1a40f8eeaf5f812.googledrive.com/host/0B1ZiqBksUHNYdEFJbUVsVUl3Ums/June%202012%20QP%20-%20Unit%205%20Edexcel%20Chemistry.pdf

Q6, why doesnt DNPH react with it, it has a C=O group :O and how do we tell it reacts with NaOH and HCl?

I think it's because C=O is in an ester group, not carbonyl (which would be attached to two alkyl groups if it's a ketone, or one alkyl and one hydrogen if it's an aldehyde)
And HCl reacts with the -NH2 group which makes this a base.
I'm not sure, but I think aqeous NaOH causes alkali hydrolysis of the ester.
:3
(edited 7 years ago)

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