Competition - post a photo you've taken of nature >>

This discussion is now closed.

Check out other Related discussions

AQAChemistry - Module 4 - Tuesday 22nd January

Scroll to see replies

http://194.34.9.21/qual/gceasa/qp-ms/AQA-CHM4-W-QP-JAN04.PDF can someone tell me why you have to half the moles of NaOH in part 3c ii

thanks!

Reply 41

RHCPfan

I just had a look at that question Maestor and i'm not really sure either.
Thanks very much for helping me out everyone.

Reply 42

Maestor

im wondering if its got to do with the volumes..hmmm

Reply 43

hey1990

Maestor

http://194.34.9.21/qual/gceasa/qp-ms/AQA-CHM4-W-QP-JAN04.PDF can someone tell me why you have to half the moles of NaOH in part 3c ii

thanks!

hi how do u get the past papers and mark schemes to this module, which are jan 2004 and earlier, plz let me knw i've dun all the others, but can find the earlier ones, thank you.

Reply 44

Maestor

http://194.34.9.21/qual/gceasa/che_assess.php

i dont bother doing the 2003 papers...answers for some questions are "updated" if you like from the ones in 2003..can get a little confusing aswell

Reply 45

MatchDancer

Maestor

http://194.34.9.21/qual/gceasa/qp-ms/AQA-CHM4-W-QP-JAN04.PDF can someone tell me why you have to half the moles of NaOH in part 3c ii

thanks!

note it says "second" in bold. If you write the equation from the origional to the second, it's
2NaOH + H2C2O4 -> Na2C2O4 + 2H20
so if you're comparing the number of mols, the number of moles of the acid is half the number of moles of the NaOH.

I'm feeling OK about it really.

Reply 46

Maestor

ahhhh rite thanks mate

Reply 47

Botticello

I hate isomers too oooh youd think they'd be easy, but I always lose marks on them!

thankk u

Preasure

7c: I think for this one you write the equation and it comes out as 2 moles of NaOH to one of propanoly chloride? I couldn't do this right either you need to use the stochiometry but I'm not sure what the equaton is.

3d: Find [H+] by using 10^-pH (antilog of pH) the use the buffer equation [H+] = Ka x ([weak acid] / [salt]) and work it so you end up with Ka = something. Then take log of that to find pKa.

Don't suppose anyones for a mark scheme for june 07 have they? Doubt it but its worth asking.

it comes out as 2 moles, as in the equation abover two acids are made, the carboxil acid and hcl, reply if u understand

Reply 50

Maestor

well GOOOOOOOOD LUCK VERYONE!!!

Reply 51

blahbloo

Man, I will never be able to pass this!!!

Reply 52

Botticello

I have officially just done craply :frown:

A C if im lucky, which is not enough! and the thought of resitting is not nice

Reply 53

Maestor

dont worry about it...resitting CHM4 in june isnt a bad thing trust me..alot of it actually comes up in CHM5 and 6 so u have to revise CH4 properly anyway..i dont think i improved on my A though.. :frown:

Reply 54

blahbloo

Hmm, Ill look forward to resitting it actually. It's not a bad module, I like it. Too bad I'm doing the coursework for this year *hmph* But Ill have more time to concentrate this year as I had to concentrate on my retakes a bit more than the A2s. Bad mistake. :P