ATAR Notes: Forum
Uni Stuff => Universities - Victoria => University of Melbourne => Topic started by: Ballerina on November 01, 2013, 01:18:40 pm
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Better late than never! If anyone has questions, feel free to post them and I (and hopefully others) will try and answer them.
1. Why isn't D = products? It seems the most stable...
(http://i.imgur.com/yBtTPTX.jpg)
2. Why does the Nernst equation switch back and forth in these examples between E = Eo + RT/F ln(conc) and E = Eo - RT/F ln(conc)?
(http://i.imgur.com/mbE2Oe1.jpg)
3. For the second one, couldn't the monodentate ligands be arranged so that they had non-superimposable enantiomers, even though there are not 4 different groups? If not, is it true that all octahedral complexes with only 3 or less different types of monodentate ligands don't display optical isomerism?
(http://i.imgur.com/034TY2U.jpg)
4. But all have n=2, which means l=1, which means ml = -1...0...1. Why wouldn't all their ml values be the same?
(http://i.imgur.com/wJTYdv6.jpg)
Thank you! :-*
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Better late than never! If anyone has questions, feel free to post them and I (and hopefully others) will try and answer them.
1. Why isn't D = products? It seems the most stable...
(http://i.imgur.com/yBtTPTX.jpg)
2. Why does the Nernst equation switch back and forth in these examples between E = Eo + RT/F ln(conc) and E = Eo - RT/F ln(conc)?
(http://i.imgur.com/mbE2Oe1.jpg)
3. For the second one, couldn't the monodentate ligands be arranged so that they had non-superimposable enantiomers, even though there are not 4 different groups? If not, is it true that all octahedral complexes with only 3 or less different types of monodentate ligands don't display optical isomerism?
(http://i.imgur.com/034TY2U.jpg)
4. But all have n=2, which means l=1, which means ml = -1...0...1. Why wouldn't all their ml values be the same?
(http://i.imgur.com/wJTYdv6.jpg)
Thank you! :-*
For your Nernst equation question...I think the system is dodgy in not being able to recognise two mathematically equivalent forms. I don't think you're wrong there. You've just used ln(p(Cl2)/[Cl-]^2)==ln([Cl-]^2/p(Cl2)), which is fine.
For the ligands question, if you have six ligands, three of them being the same and the other three being equivalent to each other, in an octahedral complex you'll always have a plane of symmetry.
I think you can arrange something of the form MA2B2C2 in a way to create optical isomers. I'm not sure if there is a general rule.
n=2 => second shell. "l" denotes the subshell; there are 2s and 2p subshells. "l" can take the value of 0 as well, don't forget. Otherwise how does hydrogen work?
"ml" denotes the orbital in the subshell. As the program said.
I'm clueless about the first one though.
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That was well explained. Thank you!
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The rate constant for the hydrolysis of sucrose is 1.85 x 10^-4 M-1 s-1 @ 25C. The activation energy is 108kJ. What is rate constant at 37C.
ln(K / 1.85 10^-4) = 0.108 / 8.31 x (1/298 - 1/310)
solve for K
someone kindly tell me what i'm screwing up here?
edit: Shit! That was silly
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Okay, so you know the temperature, gas constant and activation energy (and we're making the assumption that Ea and A don't change with temperature, which is wrong, but that doesn't matter) for two values of k.
k = Ae^-Ea/RT
OR
ln(k) = ln(A)-Ea/R(1/T)
Pick your poison and fill this equation in for both rate constants, then just divide one by the other.
Substitute the known value of k in for k1 or whatever you want to call it.
k2 Ae^-108x10^3/ 8.314 x 310
__________ ________________________
1.85 x 10^-4 = Ae^-108x10^3 / 8.314 x 298
k2 = 1.85 x 10^-4 * 5.406 (that's the value I got for the fraction on the right, I could have made a calculator error :s)
= 1.00 x 10^-3
I didn't include units but you should probably work those out on the side using the same fractions :)
Is that the right answer???
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^ That is indeed the right answer. thanks mate
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My only objection is the usage of 108*10^-3 somewhere in your working; always use SI units :P
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Use the spin-only formula to calculate the magnetic moment of a square planar complex with 4
electrons in the valence d orbitals:
Answer is 4.9 BM (4 unpaired electrons).
But I thought because it's a square planar complex it would have 0 unpaired electrons. sup wit dat
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For square planar complexes the four bottom orbitals fill as though degenerate, so you should get one electron in each of dz^2 dxy dxz and dyz - adding an electron to one of them pushes its energy above another orbital so you go to another empty one - either that or complicated quantum shenanigans that Dr. Donnelly simplified down to "just fill them as though degenerate".
also nliu1995, it eliminates the conversion error for me (I always put the decimal place in the wrong place for no reason at all) so I'll abuse the non-SI units until I die >:3
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also nliu1995, it eliminates the conversion error for me (I always put the decimal place in the wrong place for no reason at all) so I'll abuse the non-SI units until I die >:3
No no, you missed the point; the top of the fraction has *10^-3, the bottom part has *10^3 :P
For square planar complexes the four bottom orbitals fill as though degenerate, so you should get one electron in each of dz^2 dxy dxz and dyz - adding an electron to one of them pushes its energy above another orbital so you go to another empty one - either that or complicated quantum shenanigans that Dr. Donnelly simplified down to "just fill them as though degenerate".
Really...I have to know that as well...oh dear. Time to flick through my summer school notes majorly after my UMEP physics exam. I have a chemistry exam a week after my UMEP physics exam to get an exemption from first-year chemistry, and it looks like I have a LOT to cover again.
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thanks levilamp my hero
now how do I do this again?
Calculate the wavelength of light (in nanometres) required to ionise a hydrogen atom from its
ground state
quite frankly i have never felt so fkd for an exam in my life :)
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thanks levilamp my hero
now how do I do this again?
Calculate the wavelength of light (in nanometres) required to ionise a hydrogen atom from its
ground state
quite frankly i have never felt so fkd for an exam in my life :)
Ionisation energy is 13.6 eV
Use E=hc/wavelength => wavelength = hc/E
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E = -2.178 (Z^2 / n^2 (final) - Z^2/n^2 (initial) J (I MIGHT HAVE THE FINAL AND INITIAL THE WRONG WAY ROUND I'M SORRY)
Z^2 = 1 since it's hydrogen, n^2 final should be 4 and initial is 1 (single-energy-level ionisation assumed)
From the energy you can find the wavelength with E = hc/wavelength :)))))
We don't get/aren't expected to know that energy for chem, nliu :(
Remember, physics and chem do things -very- differently!
EDIT: Picked up my silly mistake in the earlier post, nliu :P
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Wait...wouldn't you have final n be infinity? Because it's ionising?
And yeah, we get given this number in VCE and UMEP physics
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I thought it was just to the next energy level. Trevor usually means that when he says "ionise the atom" (same guy who asked how many electrons an atom with quantum number n=2 and l=1 could have -.- the answer was 6 because he 'meant to say orbital').
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To "ionise" a hydrogen atom means to make it charged. The only way that can happen is to remove the electron, i.e. making the electron's final energy zero, thus freeing it.
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Oh my God I'm an idiot it's ionising wtf am I doinggggggg
Yeah it goes from n=1 to infinity then and the 1/n(initial) approximates to 0 V:
The equation should still work, though (if you're reading this, MelonBar!) - nothing else is affected by my moronic mistake.
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posting the night before the exam might be a stretch, but does anyone know if we need to know the antiperiplanar stuff for elimination reactions?
o.o its popped up on a couple exams now but i dont remember seeing anything about in the notes. :S:S not sure if it was mentioned in lectures since i don't go. OTLOTL
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hey bro, apparently you do... :/
i dont rememberlearning it on the lectures as well :(
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posting the night before the exam might be a stretch, but does anyone know if we need to know the antiperiplanar stuff for elimination reactions?
o.o its popped up on a couple exams now but i dont remember seeing anything about in the notes. :S:S not sure if it was mentioned in lectures since i don't go. OTLOTL
Yes you do. Is there anything in particular you'd like to know about it? All you really need to know is that there is a strict condition in E2 elimination that the proton abstracted by the base and the leaving group are in an anti-periplanar arrangement with respect to each other, and that sometimes this will lead to a product which violates Zaitsev's rule.
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D'8 there are exceptions to zaitstevs rule?!?! <///3333 MY LIFE IS A LIE
but i'l just remember that, thanks <3
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Good luck for tomorrow (today?), everyone!
Crossing my fingers for the questions to be friendly and reasonably simple like the 2009/2012 exams...
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I should have given nliu1995 a wig and asked him to sit the exam for me.
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I should have given nliu1995 a wig and asked him to sit the exam for me.
Dude, I haven't even done chemistry 2. I'm taking an exam in like three weeks, after my VCE and UMEP physics exam, to try and get an exemption from chemistry 1 and 2 next year due to the two weeks I spent at the ASI chemistry summer school (which actually covered everything in chemistry 1+2 plus more). Problem is, I've forgotten around half of it, so I have so much cramming to do in the week after UMEP physics.
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nliu the resident boy genius
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LOL just you wait and see my completely fail score
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DW I CRAMMED ALL OF CHEM2 IN TWO DAYS.
though i did really badly in todays exam.
it was like "hint: dont invent weird ass chemistry" and i was "HAH I HAVE NO IDEA WHAT THIS REACTION IS, LETS MAKE SOME STUFF UP AND DRAW SOME ARROWS AND MAKE A BOND HERE AND OH LOOK ILL ADD SOME HYDROGEN SURELY THATS A GOOD IDEA :'D"
H3 here i come (Y)
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I don't have lectures or the official notes to go by, just the notes I had from the summer school and my ability to decipher the notes I took.
Don't worry, that's like me in organic chemistry. I draw random arrows and hope the electrons do go there.
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haha if you want, you can have all of my chem notes for the year. theyre all annotated in colourful pens but may or may not have chocolate stains on every second page. :'D
YEAH NAH SO MANY RANDOM ARROWS MAN. except that in my case theyre actually all wrong because i really have no clue ROFL. i drew smiley faces and hearts and wrote really irrelevant side comments all over my exam paper hoping that itd distract from the REALLY BAD CHEMISTRY
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Is this you actually worried about marks or are you going to pull another surprise 91? :P
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haha deeeeffffs not a 91, my prac average this sem was appalling. my tutor took marks off every week without fail for messiness. rofl. Q n Q i was so tears.
im still hoping for a h1 but thats probably a stretch. i literally bsed my way through all of organic + quantum and had no clue what was going on in the kinetics question...which comes to like 3/4 of the paper. :'D hah this is what happens when you literally give yourself two days to study chem. including attempting to learn all of quantum;;; and i didnt even bother learning kinetics at all. i memorised the activation energy formula thingy (without even reading about how it was derived) and i walked in being like, yeah my trusty cas can solve ODEs, it'll all be gee. LOLNOPE. :'D
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I can sort of quantum and kinetics but I hate those Newman projections, stereoisomerism in organic and transition metals...organic reaction conditions...organic...organic...organic...
Notes!!?? Yesh plis :D how would you give them to me? Scan them? Wouldn't that take ages?
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Hey dudes any opinions on going from Fundamentals of Chem to Chem 2 if you are offered the chance (ie get a H1?)?
Suicide or doable?
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hell no im not scanning them rofl.
if you ever wanna drop by melbourne uni i can *physically* give them to you. OTL
id imagine its doable... i dont feel like much from chem1 helped with chem2 anyways.
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When are you going to Melbourne Uni in the next week?
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@hobbittle; not suicide, Chem 1 stuff would give you an advantage but it'd be small and you'd actually know some things BEFORE THE CHEM 1 or 2 students (like ligands which we did at the end-ish of Chem 2 @_@)
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When are you going to Melbourne Uni in the next week?
lol errday?
nah whenever, i dont mind. though i wouldve thought you'd like to get your exams over and done with first
o.o they do ligands in fundamentals? o_o XD i didnt know what a ligand was until week 12. (which didnt do me any justice for hexanaminecobaltchloride prac)
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Is around 3 on Thursday ok?
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yeah sure. um pm me or something to organise? ;;;
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Nliu and Nicola; these are the main notes by lecturers for Chemistry 2. The file is automatically deleted in 30 days. They're a pretty good indicator of the difficulty level.
http://www.filedropper.com/newcompressedzippedfolder_2
Dude, I haven't even done chemistry 2. I'm taking an exam in like three weeks, after my VCE and UMEP physics exam, to try and get an exemption from chemistry 1 and 2 next year due to the two weeks I spent at the ASI chemistry summer school (which actually covered everything in chemistry 1+2 plus more). Problem is, I've forgotten around half of it, so I have so much cramming to do in the week after UMEP physics.
lolll I know (from your grad year). I still would have given you the wig and my purse.
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Nliu and Nicola; these are the main notes by lecturers for Chemistry 2. The file is automatically deleted in 30 days. They're a pretty good indicator of the difficulty level.
http://www.filedropper.com/newcompressedzippedfolder_2
lolll I know (from your grad year). I still would have given you the wig and my purse.
O_O YAY NOOOOOTTTTTEEEEESSS!!!!!!
Do you have the chemistry 1 notes too? :D
Well...I AM doing Physics 2 right now despite being in year 12 :P
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IF YOU GUYS WANT WIGS, I CAN PROVIDE ;D
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O_O YAY NOOOOOTTTTTEEEEESSS!!!!!!
Do you have the chemistry 1 notes too? :D
Well...I AM doing Physics 2 right now despite being in year 12 :P
I didn't do Chemistry 1, unfortunately. However, the coordinator was kind enough to send the Chemistry 1 workbook my way. It has the syllabus, practice questions, and all recommended reading from textbooks. If you can do the questions and obtain the textbooks, that would be the entire course + surplus. http://www.filedropper.com/chemistry1
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Nliu and Nicola; these are the main notes by lecturers for Chemistry 2.
Hey dude thanks thats very kind :)
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XD pretty sure nliu knows chem1 fifty times better than I do anyways.
What is entropy lel
(No really, I have no clue. Only thing I learned from watching gus's lectures was that seven eleven apparently sells freddo frogs for cheaper than the food works in union house)
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I don't really know what entropy is either...I have a very vague idea of it...
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The 2nd Law: Unsustainable by Muse explains it well.
http://www.youtube.com/watch?v=EF_xdvn52As
"All natural and technological processes proceed in such a way that the availability of the remaining energy decreases.
In all energy exchanges, if no energy enters or leaves an isolated system, the entropy of that system increases.
Energy continuously flows from being concentrated, to becoming dispersed, spread out, wasted. Useless.
New energy cannot be created and high grade energy is being destroyed. An economy based on endless growth is...
Unsustainable."
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I get that bit of entropy, but what the heck do the calculations of entropy mean...does a positive standard molar entropy suggest that energy is becoming more spread out?
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I can't find a Muse song that explains that.
(But yes, it pretty much does. A positive value means entropy has occurred through a spontaneous reaction, and entropy causes molecules to spread out, diffuse, lose order. Compare an organized ionic lattice to the chaotic spread of gaseous atoms.)
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It's easy to see when it's as blatant as that, but gas-phase reactions? When we have the same number of gas particles on each side? Entropy confuses me.
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Haha Ballerina you make me laugh
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There's entropy in seemingly perfect lattices too. Entropy is difficult to grasp conceptually.
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that song confirms it. entropy is too intense for me. cant handle it. im not cut out for this
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http://en.wikipedia.org/wiki/Entropy
Me 'ead, good lord D;
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that rudolf guy has a cool beard. wish i had a cool beard </3
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http://en.wikipedia.org/wiki/Entropy
Me 'ead, good lord D;
LOL. Wiki is no good to explain such difficult concepts for some poor guy like me :P