VCAA 2012 Chemistry Unit 3 Exam Discussion

[SenriAkane]

so could you write just fractional distilation for testing if the propyl propanoate is pure ??

No. Fractional distillation isn't actually a way of testing for purity, it's a method for achieving purity.

but i said that you apply suuficent heat to vaporise the propyl propanoate and if fractions are collected before and after its impure...

Fractional distillation provides no information about the purity of you fractions. Besides you could have multiple compounds boiling at the same temperature.

[Bhootnike]

could you wright TLC for the purity question?

Don't think so, because I'm not sure whether any of the compounds could absorb UV light.
If they could though, then TLC is completely valid.

what about mass spec to determine molecular mass?

[Bhootnike]

I think A+ cut off will easily be >68 out of 75.
It wasnt that hard, and realising that it was easy in reading time meant that we shouldve taken note of providing any relevant details to our answers, such as making sure in the we had our states right, our chemical reagents, such as in the question where it asked for a chemical equation of ethene gas to ethanol (i think we shouldve added H+ or some indication of acidic media as a reagent)

mm, i cant even remember my answers for the last page of calculations. but im seriously hoping I didnt lose more than 10 marks!
 

[vagrantshades]

The solubility problem doesn't make sense to me though, because it states that some should have dissolved back into solution (0.076g/100g), so technically all the PbI2 formed wasn't precipitated, so I accounted that into my equation.

Though tbh I only lose 1 mark for that. Thank god for consequentials. Everything else was fine though!

[Deleted User]

It wasn't THAT hard. It was aight.

[Tonychet2]

Do you know what marks we are expected to get in order to achieve above 40 in chemistry?

i think u can get low A+s on both exams n get 40 or one med - high A+ and a med - high A should be 40 a

long with a+ sacs

[charmanderp]

I'm not usually one to worry about this technical stuff but how would 5-6 marks dropped on this exam + 100% on exam 2 and very high SAC scores go?

[Tonychet2]

probably like 46-49 id say 48

[charmanderp]

Based on how good my memory is and how my examiner feels about my script I could get anywhere between 72 and probably 65 haha. Fingers crossed!

[daniela.darienzo]

Oh guys, that was the most amazing exam!
I completed every question, knew exactly what I was doing and had plenty of time to spare..
Ate that exam for breakfast, lunch and tea! Can't wait for that end of year exam! Hoping to get 50! ♥ (: Yaaaaaays!
Sorry, guys, I don't mean to brag or put anyone down or anything! =/

[woliaj]

two quick questions do you guys think that they'll take of marks for writing that the components of propyl propanoate are propanol (not 1-propanol) and propanoic acid, because couldn't you make propanol with 2-propanol??
Also on the AAS graph did you have to subtract 0.06 from all of the points because of the (0,0.06)

[wallaced93]

Wondering how many marks I'd lose for incorrect states.
Also 4a I wrote propanol instead of propan-1-ol
and for 4b I just wrote the chemical equations and names of the processes (ect oxidation) instead of wording it out. Will that be ok!?   

[charmanderp]

two quick questions do you guys think that they'll take of marks for writing that the components of propyl propanoate are propanol (not 1-propanol) and propanoic acid, because couldn't you make propanol with 2-propanol??
Also on the AAS graph did you have to subtract 0.06 from all of the points because of the (0,0.06)

If you used propan-2-ol the product would be 2-propyl propanoate, so unfortunately simply stating propanol would not be sufficient.

I didn't subtract 0.06!

[WhoTookMyUsername]

(0,0.06) should be a point on your graph, i think it's already taken into account when you look at the others

[vagrantshades]

two quick questions do you guys think that they'll take of marks for writing that the components of propyl propanoate are propanol (not 1-propanol) and propanoic acid, because couldn't you make propanol with 2-propanol??
Also on the AAS graph did you have to subtract 0.06 from all of the points because of the (0,0.06)

No. It depends how you drew your graph. If your graph didn't go through the origin, you don't have to subtract 0.06. If it did, you had to make sure you subtracted 0.06 from all your absorbances. Either way, you'd get the same result!