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Edexcel A2 Chemistry 6ch04/05 JUNE 2015

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Original post by ArielHaeems
D - the acid chloride


why though?
Original post by Wahid1
Ah right yeh didn't read that part oops sorry

Basically to find the equilibrium you do the usual ICE box yeh?


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Yup,ICE box it is! :biggrin:


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Original post by HopefulDentist..


The answer is D - the acyl chloride.

The numbers in the question are there to throw you off, first of all. The only 2 acidic compounds there are the acyl chloride and ethanoic acid.
Acyl chlorides are more acidic than carboxylic acids (weak acids) because they react with water in solution to form HCl (a strong acid), thus with a lower pH like so:
CH3COCl + H2O ----> CH3COOH + HCl
Anyone doing IAL?
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ybadri
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Original post by HopefulDentist..


it will be ethanoyl chloride because when it reacts with water the cl will be lost to form hcl hence making the resulting solution acidic
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Wahid1
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Original post by Wahid1
ImageUploadedByStudent Room1433878944.462661.jpg

This is actually pissing me off!!!

Even they don't know what they're doing


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Bumpty bump someone answer this I need to sleep lol


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Reply 846
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ybadri
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Original post by AhmedBilal
Anyone doing IAL?


yes i am doing IAL
Original post by ybadri
yes i am doing IAL


How's the preparation going?
Original post by HopefulDentist..
why though?


In solution, acid chlorides react with water, e.g. ethanoyl chloride:

CH3COCl + H2O --> CH3COOH + HCl

The HCl formed makes the solution more acidic (than carboxylic acids of similar concentration)
(edited 8 years ago)
Original post by Wahid1
ImageUploadedByStudent Room1433878944.462661.jpg

This is actually pissing me off!!!

Even they don't know what they're doing


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i think its because they are using decimal places like for 0.2/0.6= the answer is 1/3 they used 0.33 . so using the exact figure we get 0.2 and they get 0.196 so its close
(edited 8 years ago)
Quick question: can you reduce a ketone/aldehyde C=O bond with excess hydrogen and a catalyst? 'Cause my notes say one thing, but a markscheme I just looked at says another :s-smilie:
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Original post by Maham88
i think its because they are using decimal places like for 0.2/0.6= the answer is 1/3 they used 0.33 . so using the exact figure we get 0.2


Makes sense now thanks!

So I wasn't wrong and this heart attack was unnecessary?


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Original post by Nautic4l
http://qualifications.pearson.com/content/dam/pdf/A%20Level/Chemistry/2013/Exam%20materials/6CH04_01_que_20130612.pdf


18ai

Questions like these, how do you know what the state symbols are meant to be?


HC2O4-(aq) + H2O(l) ----> C2O42-(aq) + H3O+(aq)

Water is a liquid obviously, and all ions are aqueous, considering they are in solution. :smile:
Original post by Wahid1
Bumpty bump someone answer this I need to sleep lol


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Change in initial moles and eqm moles oh hydrogen is 0.1. Eqm moles of HCl is 0.2 because its a 1:2 ratio between H2:h:Cl. And then you divide the eqm moles by volume(must have been stated somewhere in question).

Edit: nvm just reread the question haha


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(edited 8 years ago)
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Wahid1
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Original post by Katameringue
Quick question: can you reduce a ketone/aldehyde C=O bond with excess hydrogen and a catalyst? 'Cause my notes say one thing, but a markscheme I just looked at says another :s-smilie:


I would be inclined to say no because the reducing agent mentioned in our course is LiAlH4


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There was this point in the specification : "Carry out some experiments to link enthalpy and disorder"
Which topic is this referring to?
Original post by Wahid1
Makes sense now thanks!

So I wasn't wrong and this heart attack was unnecessary?


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haha yh i just calculated using the exact numbers and realised they were using decimals
Wooo I've never seen this question before... do you find conc of excess acid (as naOh) has been neutralised then use the acids ka to find [h+] and ka.??? Sorry not doing papers at the moment.. goinf over book 1 more time then doing papers from 1 till 12 and then asking my teacher questions on the morning good plan? Crapping it for physics unit 4 on Thursday and chem 5!!!!!:s-smilie:

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(edited 8 years ago)
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Original post by MeeraP07
Change in initial moles and eqm moles oh hydrogen is 0.1. Eqm moles of HCl is 0.2 because its a 1:2 ratio between H2:h:Cl. And then you divide the eqm moles by volume(must have been stated somewhere in question).


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We established that there's no need for the use of volumes in this scenario.

The question was about the difference in values which arises from their laziness :smile:


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Original post by AffirmedCube
HC2O4-(aq) + H2O(l) ----> C2O42-(aq) + H3O+(aq)

Water is a liquid obviously, and all ions are aqueous, considering they are in solution. :smile:


Thank you, but what about for any other questions in which they ask? Is the clue in the question usually?

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