VCE Chemistry Question Thread

[Swagadaktal]

Does anyone have any tips for remembering complementary colours? (apart from just rote-learning the hell out of the complementary colour table)

ooh not helping in any way but do we actually have to know complementary couples? I just thought that was a piece of information to help us understand the process but not actually important in terms of Study design and exam questions

[Elizawei]

b) i. All have hydroxy functional groups
ii. Glycogen, maltose and starch have glycosidic linkages (only monomer is glucose)
c) 10 ether links means 11 monosaccharides connected together. 1 water molecule removed per link, hence 10 water molecules removed. With glucose monomer, 6C, 12H, 6O --> 11x = 66C, 132H, 66O ---> Since theres 10 water molecules, that accounts for a loss of 20 hydrogens, 10 oxygens.   Thus, CxHyOz where x= 66, y= 112, O= 56
d) Do the same for 15 water molecules.

Thanks!!! 

[Elizawei]

ooh not helping in any way but do we actually have to know complementary couples? I just thought that was a piece of information to help us understand the process but not actually important in terms of Study design and exam questions

Wait, we have to know complementary colours? My teacher keeps on telling us it's out of the course haha

[Swagadaktal]

Wait, we have to know complementary colours? My teacher keeps on telling us it's out of the course haha

hls what you doing to us here buddy...
xD

[HighTide]

Does anyone have any tips for remembering complementary colours? (apart from just rote-learning the hell out of the complementary colour table)

If this is for VCE, there's no real point memorising it. It's not expected and if they want you to know something they'll tell you in the question's background info

[HopefulLawStudent]

ooh not helping in any way but do we actually have to know complementary couples? I just thought that was a piece of information to help us understand the process but not actually important in terms of Study design and exam questions

Wait, we have to know complementary colours? My teacher keeps on telling us it's out of the course haha

hls what you doing to us here buddy...
xD

If this is for VCE, there's no real point memorising it. It's not expected and if they want you to know something they'll tell you in the question's background info

Are you guys sure? My chem teacher says that the study design doesn't explicitly say we don't have to know complementary colours so it's safest if we just learn it? It's for UV vis.

[knightrider]

How would you do this question?

[@#035;3]

full equation (unbalanced bellow left out the states)
C2H5OH + O2 --> CH3COOH + H2O

Oxidation half equation:
C2H5OH-->CH3COOH     (Need to balance oxygens on LHS)
C2H5OH + H2O --> CH3COOH (Need to balance hydrogens on RHS)
C2H5OH + H2O --> CH3COOH + 4H+ (Need to balance charges)
C2H5OH + H2O --> CH3COOH + 4H+ + 4e-

Reduction half equation:
O2 -->H2O (Need to balance oxygens on RHS)
O2 -->2H2O (Then balance Hydrogens and charges)
O2 + 4H+ -->2H2O

IDK If thats right, hopefully it is...

[lzxnl]

Reduction equation doesn't have electrons?

[knightrider]

full equation (unbalanced bellow left out the states)
C2H5OH + O2 --> CH3COOH + H2O

Oxidation half equation:
C2H5OH-->CH3COOH     (Need to balance oxygens on LHS)
C2H5OH + H2O --> CH3COOH (Need to balance hydrogens on RHS)
C2H5OH + H2O --> CH3COOH + 4H+ (Need to balance charges)
C2H5OH + H2O --> CH3COOH + 4H+ + 4e-

Reduction half equation:
O2 -->H2O (Need to balance oxygens on RHS)
O2 -->2H2O (Then balance Hydrogens and charges)
O2 + 4H+ -->2H2O

IDK If thats right, hopefully it is...

Yep thats right thankyou @#035;3    just in the final line you forgot to add 4 electrons to the LHS to balance the charges 

[Swagadaktal]

Are you guys sure? My chem teacher says that the study design doesn't explicitly say we don't have to know complementary colours so it's safest if we just learn it? It's for UV vis.

What would they be examining if they tested us on complementary colours? Like surely they wouldn't try to separate the state by testing them on which colour appears in a uv vis because it didnt absorb it....
tbh I haven't come across any of those questions in an exam or in textbook But then again i haven't done that many questions. Can someone who has completed chem chime in here?

But tbh it's absurd to expect that because it's pointless. And they don't test instrumentation or the purpose of each step in the process but rather they test holistically the purpose of uv vis and when it can be utilised vs when it can't.

[Swagadaktal]

Does anyone have a summary of which technique can be used where?

Currently I can remember that:
IR spectroscopy can define what kind of bonds there are
NMR spectroscopy can be used for carbon and hydrogen environments, with high res indicating the positioning of adjacent molecules and the position of strong functional groups (i.e OH)
Mass spec can be used for molar mass and fragments of groups with diff isotopes
AAS used for metals
Gas chromatography can be used for substances below 300g that can be vaporised
HPLC can be used for all masses (anyone got a more specific use for hplc?)

What are the specified uses of
UV-VIS (is it just metals and chlorophyl coz that's all i got :O)
Thin layer chromatography

If i missed any can you guys add? And if im wrong or haven't' explained all uses please add to this as well
ty
 

[HopefulLawStudent]

UV-VIS (is it just metals and chlorophyl coz that's all i got :O)
Thin layer chromatography

From what I understand (so basically, I could be very wrong and if I am hopefully someone will correct me)...
UV-Vis is used for metal ions and coloured compounds (like chlorophyll).
TLC: typically used for nonvolatile compounds such as dyes and amino acids

[SJS]

Hi,
Just wondering what catalysts we should know for organic reaction pathways. There are some in the textbook, but it also leaves many out. 

Thanks

[Swagadaktal]

Hi,
Just wondering what catalysts we should know for organic reaction pathways. There are some in the textbook, but it also leaves many out. 

Thanks

Yo it's been a while but from what i remember - alkanol + carboxylic acid uses a H2SO4 catalyst. Alkanol to carboxylic acid utilises either Cr2O72- and H+ or MnO4- and H+. For haloalkane to alkanol must utilise OH- (although this isn't a catalyst it's a required substituent)
Erm hope this helped