Edexcel A2 Chemistry 6ch04/05 JUNE 2015 Watch

Faaiz Shah
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#941
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Can someone simplify how to read high res nmr please? I just did the 7 marker in jan 2013 and got like 4
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ArielHaeems
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(Original post by thymolphthalein)
I feel like this already came up in the thread, but I couldn't find the post.

Regarding lattice enthalpies, in the Data Booklet they are given as positive values. How do we know if we have to take them as negative values or not?

(This was relevant to the June 2014 R paper)
The true value of lattice enthalpies is always negative, however when calculating enthalpy change of solubility, for example, -lattice enthalpy is required.

(enthalpy change of solution = -lattice enthalpy + sum of hydration enthalpies)
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Faaiz Shah
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(Original post by baymax96)
I really struggle with drawing molecules from Nmr

tips? ://
Same!!!!!have u done jan 2013 7 marker. I only scrapped like 4-5 on it.
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baymax96
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(Original post by Faaiz Shah)
Same!!!!!have u done jan 2013 7 marker. I only scrapped like 4-5 on it.
noo i'm really far behind with the papers

going to have to do somewhat of an all nighter
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Faaiz Shah
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(Original post by baymax96)
noo i'm really far behind with the papers

going to have to do somewhat of an all nighter
I have only done 2 scraped an A on 2013 papers. By 1 mark hahah... Made silly mistakes in mcq
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frozo123
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(Original post by Faaiz Shah)
Can someone simplify how to read high res nmr please? I just did the 7 marker in jan 2013 and got like 4
aren't you going to sheffield hallam? 4/7 is dece
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baymax96
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when should you not include H2O in Kc/Kp
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Faaiz Shah
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(Original post by frozo123)
aren't you going to sheffield hallam? 4/7 is dece
Sheffield?? Wattt??? Nah bro chemistry is not even in my offer. What marks are u getting overall in papers??
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Faaiz Shah
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(Original post by baymax96)
when should you not include H2O in Kc/Kp
When its a weak acid.. Part dissociation.. I think
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ArielHaeems
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(Original post by baymax96)
when should you not include H2O in Kc/Kp
Whenever H2O(l) is the solvent, regardless of it being a reactant or product, it is not included in the Kc expression
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baymax96
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Also just wanted to say thank you to all the people who are replying to me, you're being so helpful but i don't want to keep spamming the thread with thank you messages:'))

very grateful for the help
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AffirmedCube
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*(d) Lithium iodide is generally much more soluble in organic solvents than lithiumchloride. Explain this observation using values of lattice energies from your data. (4 marks) [June 2012]

Can someone explain this to me. The AS recap here has thrown me off a little :eek:
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frozo123
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(Original post by Faaiz Shah)
Sheffield?? Wattt??? Nah bro chemistry is not even in my offer. What marks are u getting overall in papers??
if there's not a 7 mark nmr question or some ****
around 75-82 /90
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baymax96
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is there a fast way of knowing the answer without drawing them all out?
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AffirmedCube
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(Original post by baymax96)
Also just wanted to say thank you to all the people who are replying to me, you're being so helpful but i don't want to keep spamming the thread with thank you messages:')

very grateful for the help
Good luck and all the best. Now go off and smash that unit 4 paper!
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ArielHaeems
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(Original post by AffirmedCube)
*(d) Lithium iodide is generally much more soluble in organic solvents than lithiumchloride. Explain this observation using values of lattice energies from your data. (4 marks) [June 2012]

Can someone explain this to me. The AS recap here has thrown me off a little :eek:
The iodide ion is larger than the chloride ion, so this makes the iodide ion more polarisable than the chloride ion. This means that lithium iodide shows more covalent character than lithium chloride.

Plus, the difference between theoretical and experimental lattice enthalpy values for lithium iodide is greater than the difference between those same two values for LiCl.

Since the theoretical LE value is based off an 100% ionic model, overall this means lithium iodide is less ionic than lithium chloride, so it is less polar, and dissolves better in non-polar, i.e. organic, solvents.
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frozo123
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(Original post by ArielHaeems)
The iodide ion is larger than the chloride ion, so this makes the iodide ion more polarisable than the chloride ion. This means that lithium iodide shows more covalent character than lithium chloride.

Plus, the difference between theoretical and experimental lattice enthalpy values for lithium iodide is greater than the difference between those same two values for LiCl.

Since the theoretical LE value is based off an 100% ionic model, overall this means lithium iodide is less ionic than lithium chloride, so it is less polar, and dissolves better in non-polar, i.e. organic, solvents.
yo how do you go about this question?
Picturing what it looks like confuses me

Draw two repeat units of the polymer that could be formed from2-hydroxy-2-methylbutanoic acid.
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bbyturtlexox
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(Original post by baymax96)


is there a fast way of knowing the answer without drawing them all out?
yes, picture it in your head
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HopefulDentist..
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#959
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anyone got a document/sheet on all the organic chemistry equations for unit 4?
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thymolphthalein
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(Original post by frozo123)
yo how do you go about this question?
Picturing what it looks like confuses me

Draw two repeat units of the polymer that could be formed from2-hydroxy-2-methylbutanoic acid.
Name:  20150610_032536.jpg
Views: 433
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That's what I drew.
Edit: It's 2-hydroxy-2-methyl propanoic acid though, sorry!
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