***2013 LC Chemistry Before/After***

Hamza Malik

The third isomer is butanal itself.

KildareKing

Acciaccatura wrote: »

2-methylpropanal - CH3CH(CH3)HC=O
2-butanone - CH3C=OC2H5

Can't think of a third one

butanal itself is also an isomer CH3CH3CHO

Hamza Malik

Nl90 wrote: »

Crystallisation came up last year right!
Do you think they will bring it again?

I would expect saponification more than anything else

No recrystallation of benzoic acid came up in 2011 as q3 so its unlikely.

Water of crystallisation hasn't been up since 2006 so its a possibility as q1

Acciaccatura

KildareKing wrote: »

butanal itself is also an isomer CH3CH3CHO

Oh yeah... :rolleyes: Thanks!


Silly mistakes like that will kill me tomorrow

SecondMan

Acciaccatura wrote: »

2-methylpropanal - CH3CH(CH3)HC=O
2-butanone - CH3C=OC2H5

Can't think of a third one

Butanal's isomers are not on our course.

Hamza Malik

SecondMan wrote: »

Butanal's isomers are not on our course.

They are. It's written in my book as "You need to know the names and structures of the following table" And it shows isomers of butanal :P

simons545

Hamza Malik wrote: »

They are. It's written in my book as "You need to know the names and structures of the following table" And it shows isomers of butanal :P

Butane/butene

Hamza Malik

simons545 wrote: »

Butane/butene

And butanal. One of its isomers is shown as 2-methylpropanal C3H7CHO.

meleanor

Nl90 wrote: »

Crystallisation came up last year right!
Do you think they will bring it again?

I would expect saponification more than anything else

Crystallization hasn't been up since 06.

Acciaccatura

My dream paper/section A predictions include:

Q1- Winkler method or iodine/thiosulfate titration. If crystallization comes up I dunno what I'll do.
Q.2- Ethanoic acid/Ethanal or ethyne, it usually comes up after ethene, but it's not much to go by. Or soap.
Q.3- Rate of reaction exp. or determining heat of reaction. Hopefully

Usual stuff on Q.4, 5 and 6

A full question on water, full question on equilibrium and a full q. on gases between 7,8 and 9

10 and 11- Radioactivity, instrumentation, industrial chemistry, redox stuff is due here too, I forget the rest I'd thought of.

Nl90

Oh yeah ! I mixed between benzoic acid and water !


Please God let it be winkler

By the way the answer for WHY C.Acids are acid is this :


The electrons are drawn from the O in the OH group towards the carbonyl group " inductive effect" allows the H of the hydroxyl group to be donated.

cw67irl

I was told not to necessarily drop last years topics as if they were answered badly they could ask them again!!!

Anyone know any topics that were badly answered badly last year?

_Talia

Is anyone else extremely bucked for this? I don't know much but can't make myself study at all..

mocker2012

Between getting jury summons and chemistry, today has been fun!!

simons545

Nl90 wrote: »

Oh yeah ! I mixed between benzoic acid and water !


Please God let it be winkler

By the way the answer for WHY C.Acids are acid is this :


The electrons are drawn from the O in the OH group towards the carbonyl group " inductive effect" allows the H of the hydroxyl group to be donated.

That's only one of them
also the stability of the carboxylate ion OC=O

xJEx

I AM SO SLEEP DEPRIVED UGH. I've spent all day worrying about how i did in my physics i've done nothing for this yet I don't even know where to start... somebody ask me a question please!

simons545

xJEx wrote: »

I AM SO SLEEP DEPRIVED UGH. I've spent all day worrying about how i did in my physics i've done nothing for this yet I don't even know where to start... somebody ask me a question please!

Sure haha, I feel the same way. How did it go for you?
these were on my mock in Q.4
1. Define relative atomic mass
2. Distinguish between sigma and pi covalent bonding
3. What happens during secondary sewage treatment?
4. What are the possible shapes for molecules of general formula AB3
5. What is meant by homogenous catalysis?
6. What are mercaptans?
7. Write the conjugate acid and conjugate base of H2PO4-
8. How does nitrogen fixation occur in nature
or
8. Give an example of (i) An ionic crystal and (ii) a covalent macromolecular crystal
Your turn haha

xJEx

simons545 wrote: »

Sure haha, I feel the same way. How did it go for you?
these were on my mock in Q.4
1. Define relative atomic mass
2. Distinguish between sigma and pi covalent bonding
3. What happens during secondary sewage treatment?
4. What are the possible shapes for molecules of general formula AB3
5. What is meant by homogenous catalysis?
6. What are mercaptans?
7. Write the conjugate acid and conjugate base of H2PO4-
8. How does nitrogen fixation occur in nature
or
8. Give an example of (i) An ionic crystal and (ii) a covalent macromolecular crystal
Your turn haha

not gonna write all these out cause i'm too lazy :P think i can do most of these but what do you say for 2 and the first one in 8?

i'll give you a few :
1 - define electronegativity
2 - why is sulphuric acid added when making up iron tablets?
3 - what is Hess's law?
4 - what colour is methyl orange in a base?
5 - why do ionisation enegries decrease down the group?

Monsieur Folie

Just in case anyone is relying on them, HL Chem predictions.

Don't really need predictions tbh though. If you're stuck, do experiments and organic & whatever else you can cram in before tomorrow and you'll be fine.

xJEx

Could redox reactions of group 7 really come up as an exp Q? :O

simons545

xJEx wrote: »

not gonna write all these out cause i'm too lazy :P think i can do most of these but what do you say for 2 and the first one in 8?

i'll give you a few :
1 - define electronegativity
2 - why is sulphuric acid added when making up iron tablets?
3 - what is Hess's law?
4 - what colour is methyl orange in a base?
5 - why do ionisation enegries decrease down the group?

2. Sigma bonding is the "head on overlapping" of orbitals 2 's' orbitals, an 's' and a 'p' and 2 'p' orbitals. Can't really draw them out here, gimme a min and ill take a pic haha. Pi bonding is the weaker of the two due to less overlapping of orbitals. Pi is the "side on overlap" of two 'p' orbitals

8. The root nodules of legumes such as clover or industrial processes or the easiest one to remember is lightning.

2. Iron tablets & sulfuric acid? Prevent Iron(II) from oxidising to Iron(III)?
Not sure the exact wording of Hess' law. Something like "the heat change in a reaction is independent of the path followed and only depends on the initial and final stages"
4. Methyl orange is yellow in a base isn't it?
5. Screening effect ^^

xJEx

simons545 wrote: »

2. Sigma bonding is the "head on overlapping" of orbitals 2 's' orbitals, an 's' and a 'p' and 2 'p' orbitals. Can't really draw them out here, gimme a min and ill take a pic haha. Pi bonding is the weaker of the two due to less overlapping of orbitals. Pi is the "side on overlap" of two 'p' orbitals

8. The root nodules of legumes such as clover or industrial processes or the easiest one to remember is lightning.


Not sure the exact wording of Hess' law. Something like "the heat change in a reaction is independent of the path followed and only depends on the initial and final stages"
4. Methyl orange is yellow in a base isn't it?
5. Screening effect ^^ The others are all good

Oh yeah I remember Do you think it would be okay leaving out all of electrolysis and the atomic structure and the option?

Jackobyte

My head just feels cloudy today. Can't concentrate on anything at all. 2 exams tomorrow as well, though I don't think I'll do anything for Spanish. C'mon nice Chemistry paper!

simons545

xJEx wrote: »

Oh yeah I remember Do you think it would be okay leaving out all of electrolysis and the atomic structure and the option?

Even if you know the basics of each you should be fine. The option question should be very short anyway so that you're grand leaving.
What about the Iron(II) question? Why sulfuric acid? Prevent oxidation to Iron(III)?:P

xJEx

simons545 wrote: »

Even if you know the basics of each you should be fine. The option question should be very short anyway so that you're grand leaving.
What about the Iron(II) question? Why sulfuric acid? Prevent oxidation to Iron(III)?:P

Oh sorry, yep that's it exactly! and then you add more later to ensure a MnO4- is fully reduced to Mn2+

xJEx

Jackobyte wrote: »

My head just feels cloudy today. Can't concentrate on anything at all. 2 exams tomorrow as well, though I don't think I'll do anything for Spanish. C'mon nice Chemistry paper!

Same here. I think i'm getting sick cause I keep getting really warm and dizzy and in the exam today i kept zoning out and forgetting where i was... I'm not doing anything for spanish either, I'll just wing it and fail the listening as per usual

meleanor

OMG lads. Imagine...imagine if the flame tests came up. :')

Acciaccatura

meleanor wrote: »

OMG lads. Imagine...imagine if the flame tests came up. :')

Oh stop, there's so many beautiful possibilities that won't happen

Found a list of good finicky questions and answers, I'll post it later. You never know, it might save 6 marks :P

MarieCurie22

xJEx wrote: »

Same here. I think i'm getting sick cause I keep getting really warm and dizzy and in the exam today i kept zoning out and forgetting where i was... I'm not doing anything for spanish either, I'll just wing it and fail the listening as per usual

They got such a nice paper last year tho

simons545

MarieCurie22 wrote: »

They got such a nice paper last year tho

true wasn't expecting Boyle's law to come up 2 years in a row or the I/V Graphs tbh. Nonetheless welcome though!:D