Chemistry Exam Predictions/Thoughts (1 Viewer)

[luminol]

It's interesting how the HSC exam specifications state that at least two sub-questions in chem will be worth 7-9 marks although a lot of the school trial papers don't include huge questions/split them into bite-sized pieces. Maybe not so common in chem since an integrated spectra question can easily fill part of the quota, but still quite a handful.

 

[james049]

there were sooo many mistakes ... do they even bother proof reading it?
and there were mistakes in other cssa papers too, in software there was a question not even relevant to the syllabus

question 23 has a mistakes as well, the question says there's a peak at 88.1, but no peak can be seen for both spectrums

 

[roryg03]

It's interesting how the HSC exam specifications state that at least two sub-questions in chem will be worth 7-9 marks although a lot of the school trial papers don't include huge questions/split them into bite-sized pieces. Maybe not so common in chem since an integrated spectra question can easily fill part of the quota, but still quite a handful.

yeah was thinking about this, reckon they would ask to explain how one of the spec techniques works?

 

[CM_Tutor]

question 23 has a mistakes as well, the question says there's a peak at 88.1, but no peak can be seen for both spectrums

The peaks are small, but they are present... here is an enlarged picture of the MS:



Note that posting this image is not a copyright violation as CSSA does not hold the copyright on these... the images come from the Spectral Database for Organic Compounds, as the paper acknowledged.

 

[cassicowfan]

Regarding the CSSA 2021 paper, it should be noted that there were a lot of mistakes:

• In question 2, none of the equations are correct. The answer is meant to be D but there is a typo in the formula for aluminium carbonate. It should be Al₂(CO₃)₃ but has been incorrectly written as Al₂(CO₂)₃.
• Question 20 has no correct answer, which is 0.0124 mol L^-1. The answer given, C, is 0.00502 mol L^-1 is the concentration of lead ions in the solution when the precipitate first forms, but the question asked for the concentration in the aliquot.
• Not a mistake, but question 26(b) can be done with a variety of methods.
• Few people will notice, but the graph in question 27 is wrong. If you use the periods when the system is at equilibrium to estimate the equilibrium constant, you will find that it is roughly K = 0.097 to start with, decreases to K = 0.046 after the temperature change (which is fine), but then after the volume change it decreases again to K = 0.015. The movements in concentration following the volume change are in the right direction but they should be changes of roughly 0.25 mol L^-1.
• Question 33 begins by stating that isomers have formula C₄H₈O. There are quite a few possible alcohols with this MF, but I can't think of any that has a ¹H NMR spectrum like the one shown. Further, the question gives the relative areas for the five hydrogen environments as 3:3:2:1:1, which means the compound has 10 hydrogen atoms! There are only four possible alcohols with MF of C₄H₁₀O, one of which (2-butanol) matches the given NMR spectrum. I conclude that the question starts with the wrong formula and I wonder how many students were confused by this mistake and lost time.
• Question 34 asserts that "... whereas amphiprotic sodium hydrogen carbonate forms a solution with a pH of 1." This is preposterous, ridiculous, absurd, wrong, and total and complete bovine waste product. Sodium hydrogencarbonate is amphiprotic but is actually a weak base. If it truly had a pH of 1, its conjugate acid (carbonic acid, which is weak, pK_a = 6.8) would need to have a pH that was negative. Looking at the solutions, I have found that the question is meant to say that "sodium hydrogen sulfate forms a solution with a pH of 1." This is at least an acidic substance, and it is formally amphiprotic in that it has a conjugate acid and a conjugate base. However, having hydrogensulfate accept a proton and form sulfuric acid (which is strong, with a pK_a of -2.8) would require unusual circumstances. The hydrogensulfate ion has a pK_a of 2 and so would need to be present in a concentration of 1.0 mol L^-1 to have a pH of 1.

What are some of the other methods for q26)b?, I can only think of the method they put in their answers

 

[JesusChriiii]

Good night everyone and good luck for tomorrow! Get some good sleep tonight ! For many people it will be their last exam, all the effort will pay off eventually!

 

[icycledough]

Good luck to everyone doing Chemistry today

 

[XXXPUMPERXXX]

After that exam jumping down from a high building doesnt seem like a bad idea pls change my mind

 

[liv888]

After that exam jumping down from a high building doesnt seem like a bad idea pls change my mind

agreed it was diabolical, me bungee jumping from the harbour bridge but with no bungee seems very nice rn

 

[🍑 this is a peach]

- SIX calculations in multiple choice
- g l u c o s e
- g i b b s f r e e e n e r g y
- 2 7 markers
- ?? wtf titration
- ???? HOW keq/ksp last question???

 

[Jojofelyx]

agreed it was diabolical, me bungee jumping from the harbour bridge but with no bungee seems very nice rn

ahaha, i reckon that was about as bad as last years

 

[JesusChriiii]

ahaha, i reckon that was about as bad as last years

Really? I thought it’s even harder than lady years

 

[Life'sHard]

The last question was just maths… in chem…

 

[Life'sHard]

https://drive.google.com/file/d/14QFLQcYAv8UkAY-qj-V7QCi5bWElL4mU/view?usp=sharing

For those who enjoy getting flashbacks.

 

[bigwilly69]

trivial

 

[MyHeadee]

trivial

I'd like to echo this message 🥱

 

[🍑 this is a peach]

https://drive.google.com/file/d/14QFLQcYAv8UkAY-qj-V7QCi5bWElL4mU/view?usp=sharing

For those who enjoy getting flashbacks.

how did you take a photo of every page after you had started the multiple choice and no one notices??

 

[Siwel]

really didnt think it was that hard

 

[Jojofelyx]

really didnt think it was that hard

It was hard, but if youve done 2020 it wasnt a curveball, pretty similar in terms of the types of questions. Altho it was a bit of a pisstake with module 8, and 7. The whole exam was just mod 5 and 6 having a baby.

 

[jazz519]

I might write solutions for the paper when I get home tonight will post it on here