HSC Chemistry: Suggested Answers and Discussion

[cem123456]

We'll have our answers up and running shortly! What did you think of the paper? Any curveballs?

The paper overall wasn't bad but I'm not the best with math so definitely struggled with the seashell question!! I was wondering if the "chem of art" option answers will be uploaded too??
Thanks x

[wesadora]

For that sea shells carbonate one I got 54. something %....close enough? ;P hahaha don't know where I went wrong

yeah me and 3 other mates got 54.3%? i swear i used exact values the entire time too. :|

[jakesilove]

yeah me and 3 other mates got 54.3%? i swear i used exact values the entire time too. :|

Potentially I made a rounding error?

[wesadora]

Potentially I made a rounding error?

I see where you went wrong. 0.0295 x .25 in the first step is 0.007375, not 0.007275

[bohimei]

I used exact values and got 54.3

[jakesilove]

I see where you went wrong. 0.0295 x .25 in the first step is 0.007375, not 0.007275

Brutal; thanks for finding that mistake!

[Josh Pam]

For Q21 b) Does overall cell equation mean the net ionic equation, or like Cu + 2AgNO₃...etc?

[jakesilove]

For Q21 b) Does overall cell equation mean the net ionic equation, or like Cu + 2AgNO₃...etc?

Really good question, I didn't even think about that! I presume that you'll get the marks either way

[RuiAce]

For Q21 b) Does overall cell equation mean the net ionic equation, or like Cu + 2AgNO₃...etc?

Tbh it might mean the complete equation, which is the latter you gave.

But it might not matter here though.

[thomasdo1]

Tbh it might mean the complete equation, which is the latter you gave.

But it might not matter here though.

can you read my explanation on question 16 please (page 4 on this thread)

[RuiAce]

can you read my explanation on question 16 please (page 4 on this thread)

I did and at this point I am not acting on it yet. Because whilst it's somewhat implicit that the stimulus is useless it generally is not unless explicitly stated and I make no guarantees.

Your point is of course valid

[michellew]

(Exception: Sum of locants is the same)

when you add up all the numbers, you want your name to equal the lowest value. Both A and D are correct, but D adds up to a lower number, so is the answer

Just a note because this is my pet peeve as an org chem PhD - the IUPAC rule is that the lowest set of locants should be determined by the first point of difference, not the sum. Most of the time you get the same result (you do in this case), but sometimes you don't - this page has a good explanation: http://www.chem.ucalgary.ca/courses/351/orgnom/main/dontsum.html

[RuiAce]

Just a note because this is my pet peeve as an org chem PhD - the IUPAC rule is that the lowest set of locants should be determined by the first point of difference, not the sum. Most of the time you get the same result (you do in this case), but sometimes you don't - this page has a good explanation: http://www.chem.ucalgary.ca/courses/351/orgnom/main/dontsum.html

That implies that a textbook was written wrong, but the more likely scenario is that the syllabus is outdated as well. They can address this when the new syllabus comes.

Unless it was put into the syllabus for this year.

[Happy Physics Land]

Just a note because this is my pet peeve as an org chem PhD - the IUPAC rule is that the lowest set of locants should be determined by the first point of difference, not the sum. Most of the time you get the same result (you do in this case), but sometimes you don't - this page has a good explanation: http://www.chem.ucalgary.ca/courses/351/orgnom/main/dontsum.html

OH MY GOD MICHELLE IS THAT YOU

IM YOUR STUDENT FROM CHEMISTRY TRIAL PREP COURSE!!!

[michellew]

That implies that a textbook was written wrong, but the more likely scenario is that the syllabus is outdated as well. They can address this when the new syllabus comes.

Unless it was put into the syllabus for this year.

AFAIK the HSC/BOSTES has never said anything about what their interpretation of the IUPAC rules is, the syllabus just says that they need to be known ("identify the IUPAC nomenclature..."). For the 2012 paper when they stuffed up the multiple choice IUPAC options, the notes in the marking guidelines say "Teachers are reminded that IUPAC provides a system for the clear communication of chemical nomenclature", which I think is their way of saying "We're going with the official IUPAC rules", i.e. first point of difference since 1979. So I'm pretty sure it is a case of the textbooks/teachers being wrong and cribbing off each other for literally decades...

OH MY GOD MICHELLE IS THAT YOU

IM YOUR STUDENT FROM CHEMISTRY TRIAL PREP COURSE!!!

Lol hi!