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

MarieCurie22

Ok guys Ionisation energy is tipped for tomorrow so...heres my tricks of the trade :P



Mickeys hat and cloak represent the ATOMIC RADIUS...
-Decreasing across (Mickey's hat gets narrower):
-Increase in nuclear charge (ie more and more protons being added stronger pulling force from the nucleus, which in turn makes the radius smaller)
-Also no screening effect of inner electrons!
-Increasing Down (Like Mickey's cloak getting wider)
-Addition of new shells down the period
-Because of the addition of the new shells this means there is a screening effect of inner electrons!

Ionisation Energy:
The energy required to remove the most loosely bound electron from a neutral atom in its gaseous state.

Ionisation energies....
-Increase across the period:
-Due to the decrease in atomic radius (See above)
-Increase in atomic charge (more protons)
-Decrease down the period:
-Due to increasing atomic radius.
-Screening effect of inner electrons!

outnumbered

OH I hope this "all-nighter" pays dividends tomorrow!!!
En primer lugar, tengo El Espanol, y después, tengo la quemica!
Best of luck to all!!!

simons545

outnumbered wrote: »

OH I hope this "all-nighter" pays dividends tomorrow!!!
En primer lugar, tengo El Espanol, y después, tengo la quemica!
Best of luck to all!!!

¡Buena suerte!

ray2012

Don't know if I'll be back on this thread before the exam as I plan on studying straight until 2 .. So if not, GOOD LUCK chem students! Lets hope it's a good one.

Nl90

Can any one help me with this
How to standarise a solution ?

meleanor

Nl90 wrote: »

Can any one help me with this
How to standarise a solution ?

Titration against a primary standard and then working our its molarity.

Good luck to everyone, keep cool!

Copper_pipe

What experiments do ye reckon will come up?

ray2012

Copper_pipe wrote: »

What experiments do ye reckon will come up?

Winkler Method, Ethanal, and maybe the one about producing Oxygen with H202 or something.

Prodigious

Ethanoic acid, iodine/thiosulfate, Decomposition of H2O2

What's the winkler method?

MarieCurie22

Prodigious wrote: »

Ethanoic acid, iodine/thiosulfate, Decomposition of H2O2

What's the winkler method?

BOD of water

ladymacbeth

Prodigious wrote: »

Ethanoic acid, iodine/thiosulfate, Decomposition of H2O2

What's the winkler method?

The dissolved O2 of water is found using the winkler method

Hamza Malik

I'll kill myself is the benzoic acid experiment comes up. I don't know it well

YoursSincerely

Prodigious wrote: »

Ethanoic acid, iodine/thiosulfate, Decomposition of H2O2

What's the winkler method?

My teacher said they can't ask ehtanoic acid or ethanal in section A because sodium dichromate is banned in school labs and they can only be asked in section B

MarieCurie22

YoursSincerely wrote: »

My teacher said they can't ask ehtanoic acid or ethanal in section A because sodium dichromate is banned in school labs and they can only be asked in section B

Yes they can ask it they have it on the syllabus and thus they have every right to ask it! They are tipped to come up as they are off the syllabus next year! I went to several chem revision courses....and they all said they can definitely ask you they even went to the trouble of making dvds for the schools of these 2 experiments so know them!

ahmdoda

Hamza Malik wrote: »

I'll kill myself is the benzoic acid experiment comes up. I don't know it well

haha i didnt even do it came up 2 years in a row perior to 2012 dont see it again hopefully

MarieCurie22

ahmdoda wrote: »

haha i didnt even do it came up 2 years in a row perior to 2012 dont see it again hopefully

I dont think it will....rates of rxn or heat of rxn is your best bet there!

Quick clarification. Is it that either atmospheric or industrial chemistry will be the option?

MarieCurie22

Deleted User wrote: »

Quick clarification. Is it that either atmospheric or industrial chemistry will be the option?

Yes itll say answer either or i think

And the thinnest apparatus is always the most accurate? I.e Burette > graduated cylinder

Acciaccatura

MarieCurie22 wrote: »

Yes itll say answer either or i think

I thought it was one of A or B comes up in each option, like say our year did atmospheric and industrial but other schools did materials and electrochemistry,
then the question that comes up will have, for example, the option of atmospheric or electrochemistry. Or have I that wrong?

Either way, I only know industrial. Premier Periclase is my bítch

MarieCurie22

Deleted User wrote: »

And the thinnest apparatus is always the most accurate? I.e Burette > graduated cylinder

Not neccasaily the thinest every time....the burette is more accurate is it measures ever drop, the graduated cylinder wouldnt "read" a tiny difference like a burrette...
How ever the volumetric flask is better than any other because of its thing neck....its not the thinnest apparatus!

MarieCurie22

Acciaccatura wrote: »

I thought it was one of A or B comes up in each option, like say our year did atmospheric and industrial but other schools did materials and electrochemistry,
then the question that comes up will have, for example, the option of atmospheric or electrochemistry. Or have I that wrong?

Either way, I only know industrial. Premier Periclase is my bítch

Tbh half the schools dont bother with it....stick to what you know without the option and if you feel capable go for it!

Prodigious

Gonna nail it.

Prodigious

Gets me pumped:

https://www.youtube.com/watch?v=O9o0eNp_U_0

MarieCurie22

Prodigious wrote: »

Gonna nail it.

Thats the spirit sick of people saying otherwise...
Whats the timming today?

MarieCurie22

MarieCurie22 wrote: »

Not neccasaily the thinest every time....the burette is more accurate is it measures ever drop, the graduated cylinder wouldnt "read" a tiny difference like a burrette...
How ever the volumetric flask is better than any other because of its thing neck....its not the thinnest apparatus!

Thank you Just in this particular question I was asked either a Burette or a graduated cylinder
And I'm pretty sure you're right about the option it'll only be atmosphere or industry. Hoping for atmosphere

Prodigious

MarieCurie22 wrote: »

Thats the spirit sick of people saying otherwise...
Whats the timming today?

Timing? Never really pay attention to it, always seem to have a good 30 minutes at least at the end. I'll probably do Q4 5 and 6 first, then go back and to the experiments, and then have a look at what's left. What order are you doing?

MarieCurie22

Prodigious wrote: »

Timing? Never really pay attention to it, always seem to have a good 30 minutes at least at the end. I'll probably do Q4 5 and 6 first, then go back and to the experiments, and then have a look at what's left. What order are you doing?

Guys ALWAYS do q 4 they give you 2 "free marks" for nothing cause the total for that q doesnt add up!!SO DO Q4 ! the marks just get added on to the first 2 qs you get right! (check it out yourself....each is worth 6m x 8 = 48....q is worth 50.....:P (this has been confirmed by teachers)

MarieCurie22

Also you guys would be idiots (not saying you are yet :P) if you go into the exam not knowing:
Mn+7 = purple
Mn+4 = brown
Mn+2 = colourless

You add H2SO4 to provide protons to enure complete redution of Mn+7 to Mn+2 NOT Mn+4
Mn+4 is in the BOD expriment its the brown percipitate...
Mn+2 is a catalyst (autocatalysis!)

MarieCurie22

Prodigious wrote: »

Timing? Never really pay attention to it, always seem to have a good 30 minutes at least at the end. I'll probably do Q4 5 and 6 first, then go back and to the experiments, and then have a look at what's left. What order are you doing?

All experiments first do all if you can gives you so much space at the end
Then q 4, 7.8.9
Then the ones with the options