ATAR Notes: Forum
Archived Discussion => 2012 => Mid-year exams => Exam Discussion => Victoria => Chemistry => Topic started by: illuminati on June 13, 2012, 03:45:06 pm
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1. B
2. C
3. D
4. B
5. D
6. A
7. C
8. D
9. A
10. A
11. A
12. C
13. C
14. B
15. B
16. C
17. D
18. C
19. B
20. D
1. a) i. Glucose
ii. 2CH3CH2OH(l) + 2CO2(g)
iii. CH2CH2(g) + H2O(l) -----> CH3CH2OH (catalyst H3PO4, 300 degrees)
b) i. 3, 1
ii. stearic acid
iii. CH3(CH2)16COOH (l) + 26O2(g) ------> 18CO2(g) + 18H2O(l)
2. a) tyrosine
b) The lowest dot in the middle
c) Two of the amino acids in the first chromatogram had the same retardation factor and hence the spots had doubled up, causing only 3 dots to appear on the first chromatogram. When run in different conditions, these two amino acids separated as they had a different retardation factor under these new condition and hence two dots appeared (multiple answers accepted, but you'd have to mention the same Rf values somewhere)
3. a) Semi structural: NH2(CH2)6NH2
b) amide groups
c) Protein: carboxylic acid and amine group on the same monomers. The carboxylic acid all face one direction when polymerised. Due to this alternating fashion, every single peptide bond will be the same in terms of orietnation.
Nylon: two different monomers which contain either 2 amine groups or 2 carboxylic groups. The carboxylic groups are aligned opposite to each other on the monomer, causing the orientation to be alternating between bonds. There will be bonds where NH precedes the CO and the other bond where CO precedes NH.
Hence, differences arise in their orientation. (different answers accepted, i'd say you need to find the difference between two monomers of protein and nylon for 1 mark)
d) See the polymer below as an attachment.
4. a) propan-1-ol, propanoic acid
b) CH3CH2CH2OH (aq) + CH3CH2COOH (aq) -----> CH3CH2COOCH2CH2CH3 (aq) + H2O (l) (Catalyst H+ or H2SO4)
c) Oxidation of some propan-1-ol to propanoic acid (reagent dichromate or permaganate)
React propan-1-ol with propanoic acid (H+ or H2SO4 catalyst)
Separate the reaction mixture with fractional distillation (principles of fract. dist, use of unique boiling points)
Each one of these points should be one mark.
d) Chromatography, GC (Explanation: Use of unique retention times or retardation factor)
5. a) i. Two
ii. Three
iii. Six
b) Oxygen and hydrogen, O-H
c) Propan-2-ol
6. a) i. Draw da graph
ii. 36mg
b) IR, NMR, AAS, UV-visible, AES
i. Infra-red, Radiofrequency, Visible, UV and Visible, Visible
ii. Bonds in the molecule absorb energy that causes the bonds to change its dipole moment, qualitative (e.g. bending, twisting)
Change in nuclear spin states, discrete energy absorption, qualitative
Metals absorb a unique wavelength of light, quantative analysis can be performed based on the amount of light absorbed
Solution absorbs wavelength of the UV-visible spectrum the more concentrated it is, quantative analysis of concentration based on amount of light absorbed
Qualitative analysis. Uses the fact that a metal atom will absorb a discrete amount of energy and will release these quantas of energy as visible spectrum bands. Will not work with all metals, only those that emit visible light.
(I'd say, 1 mark qualitative or quantative, one mark for the interaction)
7. a) i. Pb(CH3COO)2 (aq) + 2KI (aq) ----> PbI2 (s) + 2CH3COOK (aq)
OR
Pb2+(aq) + 2I- (aq) -----> PbI2 (s)
ii. Ensuring that all water has been lost so that the results are accurate. (heating to constant mass)
iii. 0.09390g
iv. 0.331g
b) Lead nitrate has such a high solubility that it would dissolve in solution and hence will not precipitate (other answers accepted)
8. a) i. HCl(aq) + NaOH (aq) ----> NaCl (aq) + H2O (l)
OR
H+ (aq) + OH- (aq) ------> H2O (l)
ii. 0.00400 mol
iii. 0.00216 mol
iv. 0.0270 mol
v. 289 g/L
b) The solubility would be lower. If the burette was rinsed with water then the concentration of the HCl would be diluted. More HCl is required to neutralise the NaOH, which suggests that less NaOH reacted with the NH4Cl. Using mole ratios, NH4Cl would be lower than actual, and the concentration at saturation would be lower than actual. This in turn lowers the solubility. (1 mark for lower, 1 mark for explanation)
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You've still got it illuminati! :D
stickied :)
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7ai) do you need a 2 infront of the ch3cook? and would kch3coo be accepted
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7ai) do you need a 2 infront of the ch3cook? and would kch3coo be accepted
Yep good pick up
And it should be accepted.
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7ai) do you need a 2 infront of the ch3cook? and would kch3coo be accepted
Yep good pick up
And it should be accepted.
i wrote the ionic equations for 7a that still full marks right?
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Q5aiii) Bit obscurely worded: "In the 1H NMR spectrum, the signal at 3.6 ppm is split into a septet (7 peaks). What is the number of equivalent protons that are bonded to the adjacent carbon atom(s)?"
I gave both perspectives, but by equivalent protons does it mean other 1H protons, or 1H protons in the same environment?
I gave 0 in same environment, and 6 adjacent which cause splitting.
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7ai) do you need a 2 infront of the ch3cook? and would kch3coo be accepted
Yep good pick up
And it should be accepted.
i wrote the ionic equations for 7a that still full marks right?
Should be fine
The equation I wrote is just safer...
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Q5aiii) Bit obscurely worded: "In the 1H NMR spectrum, the signal at 3.6 ppm is split into a septet (7 peaks). What is the number of equivalent protons that are bonded to the adjacent carbon atom(s)?"
I gave both perspectives, but by equivalent protons does it mean other 1H protons, or 1H protons in the same environment?
I gave 0 in same environment, and 6 adjacent which cause splitting.
Interesting pickup
That answer you gave will get full marks
I still think 6 is just fine, vcaa examiners try to reward
but then again vcaa is dodgy so... we'll see.
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What about OH- + HCL ---> CL- + H2O?
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Q5aiii) Bit obscurely worded: "In the 1H NMR spectrum, the signal at 3.6 ppm is split into a septet (7 peaks). What is the number of equivalent protons that are bonded to the adjacent carbon atom(s)?"
I gave both perspectives, but by equivalent protons does it mean other 1H protons, or 1H protons in the same environment?
I gave 0 in same environment, and 6 adjacent which cause splitting.
Interesting pickup
That answer you gave will get full marks
I still think 6 is just fine, vcaa examiners try to reward
but then again vcaa is dodgy so... we'll see.
Yeah I'm a bit worried that vcaa examiners may resent marking my exam...I crossed out a whole question, re wrote my answer in 2 dot points in a different colour pen, legible if an effort is made to read, and wrote Refer to answer in blue pen.
Otherwise, I think I've dropped 2, possibly 3 marks :(
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What about OH- + HCL ---> CL- + H2O?
Eurgh, that is a very halfway between molecular equation and ionic.
I don't know, but i'd say if you're counting go worse case scenario and say you dropped that mark.
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What would you give my (ever so wobbly) answer for SA. 7.b)
There is not nearly enough lead to produce a ratio of 60.0g lead nitrate to 100mL water (and hence form precipitate). Thus, no lead nitrate precipitates.
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What would you give my (ever so wobbly) answer for SA. 7.b)
There is not nearly enough lead to produce a ratio of 60.0g lead nitrate to 100mL water (and hence form precipitate). Thus, no lead nitrate precipitates.
So wobbly. honestly hard to tell.
But based on current knowledge it is a possibility.
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What would you give my (ever so wobbly) answer for SA. 7.b)
There is not nearly enough lead to produce a ratio of 60.0g lead nitrate to 100mL water (and hence form precipitate). Thus, no lead nitrate precipitates.
sorry not trying to be harsh or mean but 0/1
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What would you give my (ever so wobbly) answer for SA. 7.b)
There is not nearly enough lead to produce a ratio of 60.0g lead nitrate to 100mL water (and hence form precipitate). Thus, no lead nitrate precipitates.
sorry not trying to be harsh or mean but 0/1
I wouldn't be so sure.
It's because you can argue that they have given you the solubility of the lead nitrate. Since you know that lead nitrate has a high solubility in water, you know that after the solution has become saturated you'd have a solid in there. If you had written that the solution was not saturated and therefore no excess salt crystals would be in solution that could have gotten one mark.
What he's written is just a more simplified version.
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are you sure 36 mg is not to 36.00 ? 4 sig figs?
cos i wrote 36 and everyone is telling me its 4 :/
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are you sure 36 mg is not to 36.00 ? 4 sig figs?
cos i wrote 36 and everyone is telling me its 4 :/
the absorbance is in 2 sig figs, and you need that to calculate the mass.
I'd think 2 is fine
But with that said you can only lose 1 mark for sigfigs over the whole exam, so don't fret too much
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okay i lost 1 for states already and i was like stressing
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Aww, Question 3b... I thought the answer was amino and carboxyl functional groups as it asks for the 'functional groups that link the monomers in'. I assume i was wrong?
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are you sure 36 mg is not to 36.00 ? 4 sig figs?
cos i wrote 36 and everyone is telling me its 4 :/
You won't be penalised for that. Don't think that's the sig fig qn.
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Would marks be allocated for stating that the functional groups linking the monomers together are carboxyl and amine? The question was difficult to interpret..
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Aww, Question 3b... I thought the answer was amino and carboxyl functional groups as it asks for the 'functional groups that link the monomers in'. I assume i was wrong?
I know heaps of ppl who said this including me,
not saying cause i said im right, but, its clearly coming out to be very ambiguous...
i perceived it as such, and still do. ;s
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are you sure 36 mg is not to 36.00 ? 4 sig figs?
cos i wrote 36 and everyone is telling me its 4 :/
You won't be penalised for that. Don't think that's the sig fig qn.
Would I still get the mark for writing 35 mg, even though its 1 mg off?
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Would the answer for question 1-a-i have been galactose because of the rearangement on the carbon 4 hydroxyl group from the down position to up?? :-\ :-\ :o
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Hey, I got 35mg for 6ai. I don't think I drew my graph too nicely. Will i loose a mark for that?
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Why did you get 35mg?
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I gt 350mg/L for one of the tablets. Drew my graph dodgely. Will I loose a mark for 35?
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You'll probably just lose a mark for an incorrect graph or for reading poorly off of your graph.
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Dammit, really don't want to be loosing any more. A plus cut off mark will be pretty high this year.
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I got the graph right, but I was using ratios to determine the concentration - I'm not too sure if I got 35 or 36 for my final answer.
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VCAA probably won't appreciate the use of ratios given that you were meant to have drawn a line of best fit. I don't know, my knowledge of calibration curves is regrettably sketchy.
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Is 35.5mg acceptable?
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Depends both on how you reached that figure and how VCAA marks significant figures.
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i said peptide for b) :(
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I'm almost certain that would be considered correct.
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definitely, if not more correct for proteins specifically
(although amide is 100% correct as well)
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How many marks do you reckon can be dropped for a 50?
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Oh ok. I drew the polymer in question three without the brackets around it and n outside but it still had the lines at the end cause that was my way of indicating it was continous. One mark off or nahh?
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For MC i had
5) A
12) C?
different to tony chet's answers?
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MC i had A too bazza.
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it was teh amino acid question
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both alpha helices and beta sheets are formed from the H-bonding between -NH and -CO groups, so statement II is true
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Curse you illuminati!! My solutions back in the other thread shall never be remembered :(
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also i put 0 equivalent protons :'(
4d) i put mass spectroscopy and justified it, could that be correct?
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How many marks do you reckon can be dropped for a 50?
Less than 3-4 marks I'm guessing?
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both alpha helices and beta sheets are formed from the H-bonding between -NH and -CO groups, so statement II is true
Argh this question is so stupid. Because its maintained by those functional groups, but its those specific groups that are in the peptide linkage. It can't be between any of those groups from the side chains, because that maintains tertiary structure.
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i know i dropped 2 definitely, could rise to 3-4 depending on the validity of my explanations
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both alpha helices and beta sheets are formed from the H-bonding between -NH and -CO groups, so statement II is true
Argh this question is so stupid. Because its maintained by those functional groups, but its those specific groups that are in the peptide linkage. It can't be between any of those groups from the side chains, because that maintains tertiary structure.
That's quite ambiguous indeed, if they're including or excluding the side chain groups.
However I think their intention was -NH and -CO groups inside the peptide chain (because we can't assume every protein has -NH and -CO side chain groups, although most will.)
I think D is correct, but they may accept A if they recognise the ambiguity
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is mass spec a possible answer for 4d?
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is mass spec a possible answer for 4d?
Possibly.
The thing is tho, if your sample isn't pure and you put it through Mass Spec you could get a very similar looking mass spectrum.
i know i dropped 2 definitely, could rise to 3-4 depending on the validity of my explanations
i'd think 4 marks over 2 exams for a 50. This exam was easier than last years.
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also i put 0 equivalent protons :'(
4d) i put mass spectroscopy and justified it, could that be correct?
There is debate to the meaning of "equivalent protons"
So POSSIBLY 0, don't discount it
I just can't see vcaa being so dodgy and tricking students like that
that being said it has been done before
Edit: Having re-read the question, I think they could only take 6
Because if they were equivalent protons, then you wouldn't get splitting in the first place
I think what it means is, all the protons that are adjacent to it are equivalent.
For MC i had
5) A
12) C?
different to tony chet's answers?
I don't think they'll take 5 being A tbh. 12 is C.
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could we use infrared spec for identification?
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I thought mass spec was a good idea when i was doing the exam,
cos no Mz peak at 17 or 18 (OH and H20 respectively)
i wrote next to it 6 non equivalent protons D:
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I drew the graph starting at 0 instead of .06 absorbance for some stupid reason!!! I used that date to find the mg, how many marks will I lose out of the maximum four??
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can ethanol be (aq)?
would that propyl propanoate by liquid?
could you use HPLC to seperate? (cos you wouldn't want vaporised propyl propanoate!)
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can ethanol be (aq)?
would that propyl propanoate by liquid?
could you use HPLC to seperate? (cos you wouldn't want vaporised propyl propanoate!)
I'm assuming you're referring to the fermentation question? That would indeed be aqueous, as the glucose itself was aqueous.
And propyl propanoate would be a liquid as it's relatively insoluble in water. Did you use liquid reactants?
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For 4d,
you could say that if you run the sample through mass spec, you can find its molecular mass, and compare that with propyl proponaotes molecular mass,
Right?
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(aq) probs? cos propanol and propanoic acid would be aqueous?
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For 4d,
you could say that if you run the sample through mass spec, you can find its molecular mass, and compare that with propyl proponaotes molecular mass,
Right?
that's what i said
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For 4d,
you could say that if you run the sample through mass spec, you can find its molecular mass, and compare that with propyl proponaotes molecular mass,
Right?
that's what i said
yeahhh bru!
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For 4d,
you could say that if you run the sample through mass spec, you can find its molecular mass, and compare that with propyl proponaotes molecular mass,
Right?
that's what i said
For 4d,
you could say that if you run the sample through mass spec, you can find its molecular mass, and compare that with propyl proponaotes molecular mass,
Right?
that's what i said
this reasoning is wrong because your impure propyl propanoate sample would still have a peak at its molecular mass.
and even then with your H2O and OH reasoning you're hoping that those ions are actually produced, you need to write that down too.
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For 4d,
you could say that if you run the sample through mass spec, you can find its molecular mass, and compare that with propyl proponaotes molecular mass,
Right?
that's what i said
yeahhh bru!
But how does that ensure that it's PURE? :/ Because wasn't it asking how to ensure that it's PURE propyl propanoate?
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can ethanol be (aq)?
would that propyl propanoate by liquid?
could you use HPLC to seperate? (cos you wouldn't want vaporised propyl propanoate!)
okay states is only a problem in exams if you've gotten it COMPLETELY wrong.
For GC the goal is to vaporise ....
GC is used for Mr< 300 from what i remember, HPLC could also be used.
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i specifically talked about OH and H20
i guess no way to ensure perfectly pure, but there would be OH and and H20 ions quite commonly from those i think?/
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i specifically talked about OH and H20
i guess no way to ensure perfectly pure, but there would be OH and and H20 ions quite commonly from those i think?/
It's a tough one. The thing with mass spec is that its just so much less reliable than GC and chromatography.
Like you could put IR there, and say if you see a spike at O-H then its not pure. but thats really iffy compared to others.
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5 is most probably D.
For the method of checking the sample is pure, check a similar question in the 2011 exam, question 7. Fractional distillation followed by IR spectroscopy could have been one approach, with the absence of both an OH alcohols and OH acids absorption peaks confirming purity.
Check question 2d i) in the 2010 paper for VCAA's take on the meaning of equivalent protons bonded to an adjacent carbon. Their answer for that question suggest that what they mean when they ask that sort of question is that all the protons on the adjacent carbon are equivalent to each other, but not equivalent to the protons that produced the signal for which they are causing the splitting.
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5 is most probably D.
For the method of checking the sample is pure, check a similar question in the 2011 exam, question 7. Fractional distillation followed by IR spectroscopy could have been one approach, with the absence of both an OH alcohols and OH acids absorption peaks confirming purity.
Check question 2d i) in the 2010 paper for VCAA's take on the meaning of equivalent protons bonded to an adjacent carbon. Their answer for that question suggest that what they mean when they ask that sort of question is that all the protons on the adjacent carbon are equivalent to each other, but not equivalent to the protons that produced the signal for which they are causing the splitting.
I still don't understand how it can only be D, considering that the secondary structure can only be maintained with hydrogen bonds between -NH and -CO on the amide linkage and not anywhere else in the amino acids. Because statement II doesn't account for this, it isn't entirely true.
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5 is most probably D.
For the method of checking the sample is pure, check a similar question in the 2011 exam, question 7. Fractional distillation followed by IR spectroscopy could have been one approach, with the absence of both an OH alcohols and OH acids absorption peaks confirming purity.
Check question 2d i) in the 2010 paper for VCAA's take on the meaning of equivalent protons bonded to an adjacent carbon. Their answer for that question suggest that what they mean when they ask that sort of question is that all the protons on the adjacent carbon are equivalent to each other, but not equivalent to the protons that produced the signal for which they are causing the splitting.
I still don't understand how it can only be D, considering that the secondary structure can only be maintained with hydrogen bonds between -NH and -CO on the amide linkage and not anywhere else in the amino acids. Because statement II doesn't account for this, it isn't entirely true.
The statement isn't false.
Because secondary structure IS maintained by hydrogen bonding between -NH and -CO.
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Why is the stearic acid oxidation equation worth 2 marks? States?
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@Illuminati: 6.(b). AES is also acceptable right?
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Why is the stearic acid oxidation equation worth 2 marks? States?
Realising that this form of oxidation is the same as combustion and balancing, presumably. As well as states, along with other questions.
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@Illuminati: 6.(b). AES is also acceptable right?
Not at all! So long as you explained it properly.
EDIT: AES is acceptable. I swear your post phrased the question differently when I replied to it...
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@Illuminati: 6.(b). AES is also acceptable right?
Not at all! So long as you explained it properly.
Wait are you being sarcastic? Cause you've scared the living daylight out of me.
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@Illuminati: 6.(b). AES is also acceptable right?
Not at all! So long as you explained it properly.
Wait are you being sarcastic? Cause you've scared the living daylight out of me.
You wouldn't use AES - that's used more often for identifying elements rather than organic compounds
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@Illuminati: 6.(b). AES is also acceptable right?
Not at all! So long as you explained it properly.
Wait are you being sarcastic? Cause you've scared the living daylight out of me.
You wouldn't use AES - that's used more often for identifying elements rather than organic compounds
This is question 6b, where you have to explain a spectroscopic technique. So AES is acceptable.
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almost did chromatography LOL
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Man I need to look at that exam....I haven't since 1:30 today :P
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@Illuminati: 6.(b). AES is also acceptable right?
Not at all! So long as you explained it properly.
Wait are you being sarcastic? Cause you've scared the living daylight out of me.
You wouldn't use AES - that's used more often for identifying elements rather than organic compounds
This is question 6b, where you have to explain a spectroscopic technique. So AES is acceptable.
Oh, yeah, that's fine then. As long as you mentioned that electrons get excited and produce a specific wavelength when they move down to lower energy levels.
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@Illuminati: 6.(b). AES is also acceptable right?
Not at all! So long as you explained it properly.
Wait are you being sarcastic? Cause you've scared the living daylight out of me.
You wouldn't use AES - that's used more often for identifying elements rather than organic compounds
This is question 6b, where you have to explain a spectroscopic technique. So AES is acceptable.
Oh, yeah, that's fine then. As long as you mentioned that electrons get excited and produce a specific wavelength when they move down to lower energy levels.
Yer its fine.
i'll include it now.
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Just looked at it now....wat you on about Shenz0r?
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For 4d,
you could say that if you run the sample through mass spec, you can find its molecular mass, and compare that with propyl proponaotes molecular mass,
Right?
that's what i said
For 4d,
you could say that if you run the sample through mass spec, you can find its molecular mass, and compare that with propyl proponaotes molecular mass,
Right?
that's what i said
this reasoning is wrong because your impure propyl propanoate sample would still have a peak at its molecular mass.
and even then with your H2O and OH reasoning you're hoping that those ions are actually produced, you need to write that down too.
if it was pure wouldnt it produce a molecular ion peak at a m/z value which is the same as the molar mass of propyl propanoate ?
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For 4d,
you could say that if you run the sample through mass spec, you can find its molecular mass, and compare that with propyl proponaotes molecular mass,
Right?
that's what i said
For 4d,
you could say that if you run the sample through mass spec, you can find its molecular mass, and compare that with propyl proponaotes molecular mass,
Right?
that's what i said
this reasoning is wrong because your impure propyl propanoate sample would still have a peak at its molecular mass.
and even then with your H2O and OH reasoning you're hoping that those ions are actually produced, you need to write that down too.
if it was pure wouldnt it produce a molecular ion peak at a m/z value which is the same as the molar mass of propyl propanoate ?
but even if it was impure its the same thing
you still get that peak there, cos there's still propyl propanoate in your sample.
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noo i mean, u just put the sample in the mass spec, by itself
we know the molecular mass of propyl ethanoate from its formula
get what i mean?
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noo i mean, u just put the sample in the mass spec, by itself
we know the molecular mass of propyl ethanoate from its formula
get what i mean?
yeah if its pure
but the question asks how can you determine if its pure
if your sample was pure, then you'd get the peak yeah
but if your sample was impure, then you'd still get the peak there
so you can't use parent molecular ion to determine the purity.
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I have a quick question, I would really appreciate it if you could take 2 minutes and answer it, as it's been bothering for the whole afternoon.
For the question where they asked how to produce "Propyl Propanoate" from "a pure sample of alkanol".
I interpreted "A pure sample" as "ONE sample", but instead of taking SOME propan-1-ol and oxidate half of it whilst leaving the other half as propanol, I said get some "Hex-1-ol", and I performed catalytic cracking to break it into propan-1-ol and propane, and then I made those 2 reactants.
Is this a legitimate answer?
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I have a quick question, I would really appreciate it if you could take 2 minutes and answer it, as it's been bothering for the whole afternoon.
For the question where they asked how to produce "Propyl Propanoate" from "a pure sample of alkanol".
I interpreted "A pure sample" as "ONE sample", but instead of taking SOME propan-1-ol and oxidate half of it whilst leaving the other half as propanol, I said get some "Hex-1-ol", and I performed catalytic cracking to break it into propan-1-ol and propane, and then I made those 2 reactants.
Is this a legitimate answer?
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Oxidise* and Hexan-1-ol* you get the point
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wouldn't think so, sorry :\ question is pretty clear IMO
though you'll only lose 1 mark i reckon so long as all your other steps are correct
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1aiii) did we have to state the catalyst to get the mark?
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1aiii) did we have to state the catalyst to get the mark?
yes.
i think this one asked for a catalyst.
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Hey for the identification of whether the sample is pure or not, can you write that IR spec. can be used and the fingerprint region can be compared of the sample produced with a pure sample of propyl propanoate, on the spectra? Would this be a sufficient response for gaining the 2 marks?
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With that identification of pure sample question, is HPLC acceptable?, and if not would i still at least get a mark for my explanation: run a HPLC chromatogram and if one spot appears, it's pure, if two or more spots appear it's not pure?
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With that identification of pure sample question, is HPLC acceptable?, and if not would i still at least get a mark for my explanation: run a HPLC chromatogram and if one spot appears, it's pure, if two or more spots appear it's not pure?
I thought HPLC produced a chromatogram with retention times and peaks not spots?
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Oh crap... lol so would i still get a mark for the explanation? since it's a correct explanation for GC right? lol what was i thinking... i knew IR was the answer but thought that choosing HPLC would allow me to write a more concise response...
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apparently stuff like TLC and GC were the more appropriate answers
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So hplc wouldn't be correct? :(
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For the first question of ahort answer where it asked for the monomer, I said beta-glucose instead of glucose. Is that still acceptable?
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What about using sodium carbonate and seeing if any bubbles (CO2) have appeared. But i wrote that this would indicate that their are some excess acidic reactants (propanoic acid AND propanol) still present so sample wouldn't be pure. But i don't think the alcohol actually reacts with sodium carbonate anymore. Will i get any marks at all :/
And yep ^ that would be accepted.
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was it necessary to be so detailed in your response to the spectroscopic technique question. I chose AAS and simply said its interaction was that visible light is absorbed by atoms as it promotes electrons to a higher energy level and that the amount of absorption indicated the concentration of the atoms present.
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was it necessary to be so detailed in your response to the spectroscopic technique question. I chose AAS and simply said its interaction was that visible light is absorbed by atoms as it promotes electrons to a higher energy level and that the amount of absorption indicated the concentration of the atoms present.
that should be fine and wotrh 2 marks
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can HPLC be used to seperate propyl propanoate :S?
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For the first question of ahort answer where it asked for the monomer, I said beta-glucose instead of glucose. Is that still acceptable?
It's more than acceptable, it's even better as an answer! Definitely get full marks for that.
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oh sh!! wrote O-H not oxygen and hydrogen :'(
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wtf do you lose marks for writing O-H??
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I wrote O-H and write next to it oxygen and hydrogen.. would that be right?
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I wrote O-H and write next to it oxygen and hydrogen.. would that be right?
that should be right, i wrote
oxygen, hydrogen (O-H)
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fml, should have read the exam
may squeeze in for low A+ if i'm lucky
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was it necessary to be so detailed in your response to the spectroscopic technique question. I chose AAS and simply said its interaction was that visible light is absorbed by atoms as it promotes electrons to a higher energy level and that the amount of absorption indicated the concentration of the atoms present.
that should be fine and wotrh 2 marks
probably should have said it was metals.
With that identification of pure sample question, is HPLC acceptable?, and if not would i still at least get a mark for my explanation: run a HPLC chromatogram and if one spot appears, it's pure, if two or more spots appear it's not pure?
yeah, the fact you said spots throws it off a bit...
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You won't have lost marks for saying an O-H bond was present, as they are the atoms that the IR spectroscopy showed. It ain't an english exam brethren.
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Does anyone know what the marking would be if you had the equations right but the balancing wrong??
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Does anyone know what the marking would be if you had the equations right but the balancing wrong??
Balancing? 0/2 :( marking scheme says that you only get the states mark if you get the balancing right. sorry!!!
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For the Question 7a writing the lead ionic equation, can you write +2K plus on the end and clearly indicate its a spectator ion in the reaction?
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Hi, is there anywhere I could get the chem questions cause' i couldn't remember my answer without looking at the questions.
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Hi, is there anywhere I could get the chem questions cause' i couldn't remember my answer without looking at the questions.
link to exam here: VCAA 2012 Chemistry Unit 3 Exam Discussion
:)
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does the calibration curve have to go through the origin?