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Aqa chem 4/ chem 5 june 2016 thread

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tsr.png can someone help me understand this
CDCl3 the solvent used for nmr. What the hell is the D?
Original post by SirRaza97
CDCl3 the solvent used for nmr. What the hell is the D?


Deuterium.
Original post by Parallex
Deuterium.


But then this solvent isnt proton free?
Original post by SirRaza97
But then this solvent isnt proton free?


CDCl3 i dont see no protons and you can use CCl4 too
Original post by Sniperdon227
tsr.png can someone help me understand this


I think it has to do with the fact it's a 2 step nuetralisation process. So half the acid is nuetralized at step 1 and the other half at step 2? I am not too sure. Maybe the overall equation might give some idea?

H2C2O4 + 2NaOH ---->Na2C2O4 + 2H2O
Original post by Sniperdon227
CDCl3 i dont see no protons and you can use CCl4 too


The D is is proton rich isnt it? It's just a hydrogen isotope.
Original post by SirRaza97
But then this solvent isnt proton free?


There isn't a peak for deuterium in the same range as hydrogen. (quoted from the book) P150.
Reply 448
Original post by Lilly1234567890
What do we need to know about the M+1 peak?


All i know is that it has the highest mass/charge ratio so is on the right of the molecular ion peak, and is caused by the C-13.
To what extent do we need to know chromatography?
Do we need to know two step titrations
Original post by sockface
Do we need to know two step titrations


I think that's just unit 5
Original post by SirRaza97
The D is is proton rich isnt it? It's just a hydrogen isotope.


The reason CDCl3 is used instead of CHCl3 as a solvent in Proton NMR is because it doesnt interfere with the results, dont think you need to know anything else, Deuterium is just an isotope of H, with double the mass.
Can someone please explain to me why an anhydride is less likely to be hydrolysed than an acyl chloride?
Reply 454
Original post by Sniperdon227
tsr.png can someone help me understand this


its ethandioc acid so for every 1 mole of doic acid 2x H+ are released. This means you need double the amount of OH- for every mole of ethandioc acid.

you know the number of moles of OH- used. (vol x conc)
then half it to get moles of ethandoic acid
then moles ethanoic acid/ volume = conc

:smile: hope that helps
Reply 455
Original post by 12284
All i know is that it has the highest mass/charge ratio so is on the right of the molecular ion peak, and is caused by the C-13.


not just C13 but isotopes in general.
How do you work out fragmentated ions?
Reply 458


each concentration is halved if vol doubled. now you can use the rate equation or divide the rate by 8
Why does the molecular ion have the same mr as the compound?? Surely if it's an ion and there is one electron knocked off, its mr should be lower?

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