[Tantail]

(Original post by Bi0logical)
You know for example when it says Copper (II), I understand it has a 2+ charge but how do u know whether whatever is in the brackets is negative or positive? will it always be + ??

For a metal it is always positive. And in my experience with questions like that they always seem to be positive if it's shown in brackets

[master_blaster66]

f335 is really too hard...im struggling with buffer calculations and ph calculations...and on the top its synoptic WTH

[navarre]

(Original post by master_blaster66)
f335 is really too hard...im struggling with buffer calculations and ph calculations...and on the top its synoptic WTH

Yeh they are the hardest bit. Whenever I get them I have forgotten them by the next day, as anything mathsy is easy to forget.

For synoptic, just remember bond angles/shapes (they love that), each technique, especially colorimetry, titrations, reflux and chromatography, and most of the reactions/functional groups from F334.

[Princess Kawaii]

Why does it feel like I get the stuff yet I don't get the stuff

[Princess Kawaii]

For pH calculations: what are the two assumptions we make? and which of the two lead to greatest inaccuracy?

[sunshinesmile10]

(Original post by Princess Kawaii)
For pH calculations: what are the two assumptions we make? and which of the two lead to greatest inaccuracy?

one assumption (for weak acids) is that the H conc = the A- conc since both came from the acid itself. Also you assume that the conc of the acid at equilibrium is the same as the original concentration because it only dissociates slightly.
The second one leads to most innaccuracies( i think)

[301lw]

i don't mind all of the ph things, its just learning all of the reactions again there's so many!

[agyawali]

(Original post by Princess Kawaii)
Why does it feel like I get the stuff yet I don't get the stuff

looooooooool this made me laugh!!!!!!

agreed though!! i feel like i know every thing and when it comes to doing the paper im like WTF!

[Toshiya]

(Original post by Princess Kawaii)
Why does it feel like I get the stuff yet I don't get the stuff

I know that feeling! I keep doing the papers and then realising that I don't know half as much as I thought I did.

The occasional random synoptic question keeps catching me out too...

[SimpleGirl]

(Original post by Toshiya)
I know that feeling! I keep doing the papers and then realising that I don't know half as much as I thought I did.

The occasional random synoptic question keeps catching me out too...

Same
When I'm revising the topics, I feel confident but then when I do a paper I can't answer some of the questions fully so don't get as many marks as I should.

[master_blaster66]

(Original post by SimpleGirl)
Same
When I'm revising the topics, I feel confident but then when I do a paper I can't answer some of the questions fully so don't get as many marks as I should.

yeee agrreed..its hard to get full marks on the big marker questions

[Toshiya]

I'm really starting to panic, I have physics the monday before and I really can't do most of the syllabus for that so that needs loads of work too. Still, when I panic I tend to work harder so this might be a good thing...

[301lw]

can someone please explain how to work out the half equations in the nitrogen cycle?

[mimsicle]

June 2010


Q 2d) t-Butanol has a lower boiling point than butan-1-ol. Explain this in terms of intermolecular bonds.

- Instantaneous dipole - induced dipole
- Less energy is required to separate t-butanol molecules
- Due to t-butanol molecules not being able to get as close together


I understand this question and the answer but I just can't quite understand why is the I.M force instantaneous dipole - induced dipole? At first I thought it was permanent dipole but I kind of understand why that isn't but now I'm thinking surely it's hydrogen bonding?

Get the feeling I'm being really stupid and when someone tells me the answer I'll be like "oooohh yeah!" any help appreciated!

[Waqar.]

(Original post by Princess Kawaii)
For pH calculations: what are the two assumptions we make? and which of the two lead to greatest inaccuracy?

That's actually one of the questions from one of papers so I'd suggest checking the mark scheme to know the exact answer they're looking for. Hope that helps

[Tantail]

(Original post by mimsicle)
June 2010


Q 2d) t-Butanol has a lower boiling point than butan-1-ol. Explain this in terms of intermolecular bonds.

- Instantaneous dipole - induced dipole
- Less energy is required to separate t-butanol molecules
- Due to t-butanol molecules not being able to get as close together


I understand this question and the answer but I just can't quite understand why is the I.M force instantaneous dipole - induced dipole? At first I thought it was permanent dipole but I kind of understand why that isn't but now I'm thinking surely it's hydrogen bonding?

Get the feeling I'm being really stupid and when someone tells me the answer I'll be like "oooohh yeah!" any help appreciated!

Because the t-butanol molecules can't get close enough together [because it's an isomer I guess it's one of those crooked ones?], they can't hydrogen bond, so only id-id bonds can form. For hydrogen bonds need molecules to be pretty close. I'm pretty sure that's why. Hope that makes sense

[mimsicle]

(Original post by Tantail)
Because the t-butanol molecules can't get close enough together [because it's an isomer I guess it's one of those crooked ones?], they can't hydrogen bond, so only id-id bonds can form. For hydrogen bonds need molecules to be pretty close. I'm pretty sure that's why. Hope that makes sense

Oh right I see, but then why couldn't a permanent dipole form? Being stupid again thanks a lot! I've never disliked an exam as much as this one ._.

[Mathlete 4 the win]

(Original post by Tantail)
Because the t-butanol molecules can't get close enough together [because it's an isomer I guess it's one of those crooked ones?], they can't hydrogen bond, so only id-id bonds can form. For hydrogen bonds need molecules to be pretty close. I'm pretty sure that's why. Hope that makes sense

I'm just guessing here but maybe they can both hydrogen bond as I can't perticularly see a reason why not.
But the instantaneous dipole - induced dipole bonds in the butan-1-ol molecule is stronger because they can pack closer together and there's more point of contact. So although they both have hydrogen bonding the higher boiling point is due to the addition of strong instantaneous dipole - induced dipole bonds.

What d'ya reckon?

[mimsicle]

(Original post by Mathlete 4 the win)
I'm just guessing here but maybe they can both hydrogen bond as I can't perticularly see a reason why not.
But the instantaneous dipole - induced dipole bonds in the butan-1-ol molecule is stronger because they can pack closer together and there's more point of contact. So although they both have hydrogen bonding the higher boiling point is due to the addition of strong instantaneous dipole - induced dipole bonds.

What d'ya reckon?

Perhaps, but I would have thought the mark scheme would have mentioned hydrogen bonding. All it said in terms of the actual bonds was i.d-i.d. I understand the chemistry of this course (for the most part), just struggling to get to grips with these mark schemes that constantly change -.-

[sunshinesmile10]

tbh///id-id bonding is pretty standard for everything. Whenever your talking about intermolecular bonding its a good idea to chuck that in. I agree about the mark schemes....
do we have to know all the reactions of the nitrogen cycle??
how are you all managing this...or are you?