**Chemistry...Before/After

reznov

Mista wrote: »

Don't be stupid.

Oh you want an A1?
Aren't you grand with a B2? What happened to modesty?

LanaMay94

paddyhes wrote: »

Anybody know where you can get a list of all the definitions?

Theres a list of all definitions in alphabetical order under the chemistry section of skoool.ie

DepoProvera

LanaMay94 wrote: »

Theres a list of all definitions in alphabetical order under the chemistry section of skoool.ie

Just had a quick browse of them... Some of them are quite lacking for eg: Strong acid
An acid that is fully dissociated in solution(should include a good proton donor)

Activation energy
The minimum amount of energy which colliding molecules must have before they can react together.(I think the phrase "for a reaction to occur" was specifically disallowed in a recent marking scheme... Should be "for an effective collision to occur"

paddyhes

DepoProvera wrote: »

Just had a quick browse of them... Some of them are quite lacking for eg: Strong acid
An acid that is fully dissociated in solution(should include a good proton donor)

Activation energy
The minimum amount of energy which colliding molecules must have before they can react together.(I think the phrase "for a reaction to occur" was specifically disallowed in a recent marking scheme... Should be "for an effective collision to occur"

yeah thought the same.

leaveiton

What does everyone reckon the most important things to focus on are? I'm covering everything, but I've still a bit to do tomorrow/Tuesday morning so I can't do it all in the same detail. I'm planning on focusing on all the experiments, organic, stuff that can come up in Q5 (Trends, bonding, history etc), rates, equilibrium, water, pH, and a couple of other things. I'll look at everything else too but probably won't spend as much time on it.

Pepperr

To anyone doing some last minute cramming, I would suggest taking tomorrow and Tuesday morning to look at all of the experiments, the questions practically repeat themselves in what they can ask (Specifically the Q1 and Q2, Organics and volumetric). Then maybe glance over some of the others if you have time (Methanol and platinum/NaOH and HCl heats of reaction) I will be leaving out the Benzoic acid one, since it came up last year and is a pain in the hole :P

If you know a little bit about the whole course you can do well in the Q 4 depending on the questions asked.

I personally find the organics non experiments questions easy enough, learn the different mechanisms, the types of reactions and the reagents needed for each.

Fuels is a nice handy one and is relatively short. Look over oil fractional distillation, the additives, the processes (for octane number AND methods of getting Hydrogen) and the definitions.

Look over how to draw a graph, and putting the right variables on the right axes, if it comes up it usually has a lot of marks for relatively little effort. Learn the definitions of rates of reaction and the different types of catalysis.

Finally look over the first few chapters with all the guys, radiation and those sorts of things (structures of atoms etc) and learn the definitions.

If you have time, learn the gas laws and those experiments.

I know I pretty much listed the whole course except the optionals and some of the odd questions, but if you know them well you are pretty much guaranteed to do well. Easily covered in the day and a half we have left. Hope it helped someone, good luck to all!

LanaMay94

DepoProvera wrote: »

Just had a quick browse of them... Some of them are quite lacking for eg: Strong acid
An acid that is fully dissociated in solution(should include a good proton donor)

Activation energy
The minimum amount of energy which colliding molecules must have before they can react together.(I think the phrase "for a reaction to occur" was specifically disallowed in a recent marking scheme... Should be "for an effective collision to occur"

I don't really rely on that list, but the definition for activation energy is the same in my book I think. I've always said for a reaction to occur. Would that definitely be marked wrong?

Random_Person

I've hit a new level of procrastination, I've convinced myself that this thread makes up for the fact that I'm on the internet because it's somehow helping me to study..

it really isn't

DepoProvera

LanaMay94 wrote: »

I don't really rely on that list, but the definition for activation energy is the same in my book I think. I've always said for a reaction to occur. Would that definitely be marked wrong?

Have a look at Q4 in 2010 and 2011. It would be allowed in 2010 but is specifically disallowed in 2011. So it's basically up to how the marking scheme goes on the day, but if I were you I'd go with the options that were accepted both years, or more specifically the options that were accepted most recently.

DepoProvera

I have a feeling, no idea why, that longish questions will come up concerning: describing how the mass spectrometer works and something about esters! Just putting it out there..

Pepperr

Just a helpful tip on the mass spec, might be handy to remember the mnemonic:

Vodka Is A Strong Drink

Vaporisation, Ionisation, Acceleration, Separation and Detection.

A common question is about the principle on which they work, which is that ions can be separated by mass while moving in a magnetic field!

Lighter ions are deflected more than heavy ones, which causes the spread.

Uses: Determining mass/abundance of isotopes. Analysing gases from a waste dump/ organic pollution in water!

leemurta

Mista

^ The acid goes in the burrette :pac:

leemurta

Mista wrote: »

^ The acid goes in the burrette :pac:

Yeah, but the base goes in the burette for one of the titrations with phenolphthalein.

Mista

leemurta wrote: »

Yeah, but the base goes in the burette for one of the titrations with phenolphthalein.

The ethanoic acid one? Still goes in the burette :pac: I think sodium hydroxide causes the tap to stick

EDIT: Just looked it up, it can go in either

Also, does anyone know of any way (rhyme, etc..) to remember the gas laws?

DepoProvera

Mista wrote: »

The ethanoic acid one? Still goes in the burette :pac: I think sodium hydroxide causes the tap to stick

EDIT: Just looked it up, it can go in either

Also, does anyone know of any way (rhyme, etc..) to remember the gas laws?

I always differentiate Boyle and Charle's Law by thinking Boyle does the opposite of what you might think(he doesn't adjust the temperature, he keeps it constant).. Pretty lame way to go about it but it works for me...? :P

David1994

Lads this is the make or break exam for me.If I dont get a C1 I don't I will get my points... Absolutely terrified!

Mista

DepoProvera wrote: »

I always differentiate Boyle and Charle's Law by thinking Boyle does the opposite of what you might think(he doesn't adjust the temperature, he keeps it constant).. Pretty lame way to go about it but it works for me...? :P

Haha, thats pretty good actually :P Thanks

anBoMor

I'm not entirely sure why I chose Chemistry, having amazingly failed Science in the aul JC.. It drives me up the wall, I know I'm intelligent but the subject just kills me! I can get an A1 one day on a test and get a D3 the next, it's so confusing to me.

Hayezer

Few questions..

• You know in oxidation and reduction where they say "using oxidation numbers or otherwise to balance the equation", can you literally just balance it like you would any other equation? Our old teacher did a big long, complicated way of doing it, but my new one says you can just slot in numbers? Dunno if I really trust her!
• When working out heat of combustion, do you just add the values of the products and take them away from values of reactants? Again, this is how old teacher did it, now new teacher does a more complicated way!

Thanks!

DepoProvera

Hayezer wrote: »

Few questions..

• You know in oxidation and reduction where they say "using oxidation numbers or otherwise to balance the equation", can you literally just balance it like you would any other equation? Our old teacher did a big long, complicated way of doing it, but my new one says you can just slot in numbers? Dunno if I really trust her!
• When working out heat of combustion, do you just add the values of the products and take them away from values of reactants? Again, this is how old teacher did it, now new teacher does a more complicated way!

Thanks!

For the first question, I always thought you couldn't do it by normal methods, but I looked at 2 examples (2007,2008) and it seems to work! :L I'd say if you can, go for it.

For the second, are you talking about Hess' law calculations? I don't really understand your question

Mista

Hayezer wrote: »

Few questions..

• You know in oxidation and reduction where they say "using oxidation numbers or otherwise to balance the equation", can you literally just balance it like you would any other equation? Our old teacher did a big long, complicated way of doing it, but my new one says you can just slot in numbers? Dunno if I really trust her!
• When working out heat of combustion, do you just add the values of the products and take them away from values of reactants? Again, this is how old teacher did it, now new teacher does a more complicated way!

Thanks!

Oxidation and reduction I'm fairly certain you have to do a simultaneous to balance out the electrons.

I also do heats of combustion in a fairly long way, don't know any other way to do it. But I think I seen something like what you mentioned in the marking scheme.

Hayezer

DepoProvera wrote: »

For the first question, I always thought you couldn't do it by normal methods, but I looked at 2 examples (2007,2008) and it seems to work! :L I'd say if you can, go for it.

For the second, are you talking about Hess' law calculations? I don't really understand your question

2002 Question 8 part e) sorta thing :P Calculating heat of combustion given heats of formation

DepoProvera

Hayezer wrote: »

2002 Question 8 part e) sorta thing :P Calculating heat of combustion given heats of formation

Ah right! Yeah it's accepted by the marking schemes.. However, my teacher says that the other method is better because you are able to know if you've screwed up if things don't cancel.

Hayezer

I did out 2002 in the way I'm talking about and it seemed to work.

Products minus reactants.
8(-394)+10(-286) - 2(-125)+13(0)
Equals -5762
Since it's 2Butane, dividde by two.
Answer:-2881

That's how I do em anyway :L

DepoProvera

Hayezer wrote: »

I did out 2002 in the way I'm talking about and it seemed to work.

Products minus reactants.
8(-394)+10(-286) - 2(-125)+13(0)
Equals -5762
Since it's 2Butane, dividde by two.
Answer:-2881

That's how I do em anyway :L

If it works, stick with it! Don't go changing your methods at this point

abbeymate

Hi guys, just wondering if anyone knows if its ok to simply write the formula of chemicals rather than naming them, especially for experiments?? Not much time left to be spending on anything non essential :-P

DepoProvera

abbeymate wrote: »

Hi guys, just wondering if anyone knows if its ok to simply write the formula of chemicals rather than naming them, especially for experiments?? Not much time left to be spending on anything non essential :-P

Yeah it's fine. Just look out if they ask to identify(either formula or name), name(only name), give the formula(obviously the formula :P). Usually they'll accept either in any case, but it might be something they crack down if they need to alter the marks.

But whatever you do, don't give both the name and the formula unless specifically asked to do so. Write down the one you're most confidant with as cancelling will, I assume, apply!

Liveforrugby

anBoMor wrote: »

I'm not entirely sure why I chose Chemistry, having amazingly failed Science in the aul JC.. It drives me up the wall, I know I'm intelligent but the subject just kills me! I can get an A1 one day on a test and get a D3 the next, it's so confusing to me.

You'll get an A1. Optimism is key. You gotta believe!

abbeymate

Yeah it's fine. Just look out if they ask to identify(either formula or name), name(only name), give the formula(obviously the formula :P). Usually they'll accept either in any case, but it might be something they crack down if they need to alter the marks.

But whatever you do, don't give both the name and the formula unless specifically asked to do so. Write down the one you're most confidant with as cancelling will, I assume, apply!



Thanks very much! Now if you can tell me what's coming up I'd be even more appreciative!! ;-) :L