F334 (19/06/2013 9:00AM) - Salters Chemistry (Chemistry of Materials) Revision Thread

Original post by tsr1

C14H12O3 + 3OH- ----> (C14H9O3) 3- + 3H2O

can someone please explain why we get C14H9O3) 3- ?

3 OH groups that can donate 3 protons/hydrogen atoms to the base (OH-), so you're left with 3 negative oxygen atoms, giving a minus charge of 3.

Reply 45

tsr1

Original post by abzy1234

3 OH groups that can donate 3 protons/hydrogen atoms to the base (OH-), so you're left with 3 negative oxygen atoms, giving a minus charge of 3.

3 OH on the alcohol will donate the H+ isn't? and thanks it was just in an equation form which made it harder for me to understand.. :smile:

Reply 46

Original post by tsr1

3 OH on the alcohol will donate the H+ isn't? and thanks it was just in an equation form which made it harder for me to understand.. :smile:

Yup and no problem :biggrin:

Reply 47

CureSam

Original post by tsr1

3 OH on the alcohol will donate the H+ isn't? and thanks it was just in an equation form which made it harder for me to understand.. :smile:

Be careful, a hydroxyl group on an alcohol won't donate a proton, only a cardboxylic acid.

Reply 48

suncake

Original post by CureSam

You must have got like 90% ums on that?

Nope

74/90 raw marks was 76/90 ums, so about 84% ums.

Original post by gingernat

Brilliant, thanks for uploading. The paper actually didn't seem too bad, just those god-awful grade boundaries that put my two grades below where I needed.

Could you explain 2(c)(iii)? I don't understand why ethanoic acid can hydrogen bond, but compound D only has pd-pd bonding.

Thanks loads if you can. :biggrin:

No bother

Carboxylic acids can form hydrogen bonds with each other because of the OH in the COOH group.

Esters like compound D however do not contain an OH group, so don't have a suitable slightly positive hydrogen that can bond to the slightly negative oxygen on their carbonyl group. The hydrogens on the CH bond can't form H bonds because C and H have similar electronegativities, so it's not a polar bond and the H isn't slightly negative.

I hope that made sense (and is actually correct :ninja:

)... I hate intermolecular bonds :lol:

Reply 49

tsr1

Original post by CureSam

Be careful, a hydroxyl group on an alcohol won't donate a proton, only a cardboxylic acid.

u make sense but the question said its an alcohol... confused

Reply 50

Kreayshawn

How do we calculate the rate of disappearance? Last question on Jan13

Reply 51

tasniaa

Now for F334.

Posted from TSR Mobile

Reply 52

super121

5

Original post by tasniaa

Now for F334.

Posted from TSR Mobile

Today's paper was good practice for mass spec :tongue:

Reply 53

Tomatochuckers

18

Original post by tasniaa

Now for F334.

Posted from TSR Mobile

This paper is the bane of my life

Got AAA in the AS units
an A(*) in A2 coursework, a mid B in Chem of Design
all the above being first attempts
yet a E then D then C in chem of mateirals
resulting in a B overall

:angry:

Reply 54

11hokj1

does anyone have the Jan 2013 MARK SCHEME? :biggrin:

Reply 55

super121

5

Original post by 11hokj1

does anyone have the Jan 2013 MARK SCHEME? :biggrin:

Here you go :smile:

F334 Jan 2013.pdf97.4KB

Reply 56

11hokj1

Original post by super121

Here you go :smile:

Thank you. And good luck next week! :biggrin:

Reply 57

I'm literally sick with all the chemistry revision. Constantly regurgitating stuff one learnt from last year certainly ain't fun :tongue:

Reply 58

11hokj1

Original post by abzy1234

I'm literally sick with all the chemistry revision. Constantly regurgitating stuff one learnt from last year certainly ain't fun :tongue:

Same here. And I absolutely hate F334. Thought it was harder than F335! But yesterday's F335 was horrible too :frown:

Reply 59

Original post by 11hokj1

Same here. And I absolutely hate F334. Thought it was harder than F335! But yesterday's F335 was horrible too :frown: