HSC Chemistry Question Thread

[RuiAce]

I thought for maths, notes are helpful at first when you're getting introduced to new abstract ideas and then over time you don't need it as much

Notes, I thought were only good for basic understanding for physics and chemistry and over time, it wouldn't be needed as much

Some people use it. I never had notes for maths personally.

Yeah that's the point. That's why I say "gradually" shift to past papers. But at least notes helps me check up on what I don't know when I get stumped on a past paper qn.

[karenc.]

Hi everyone, I am just wondering if you guys have any questions for ppm calculations because I sometimes get them wrong in exams. Many thanks Karen.

[jakesilove]

Hi everyone, I am just wondering if you guys have any questions for ppm calculations because I sometimes get them wrong in exams. Many thanks Karen.

Maybe you could find some questions that you've gotten wrong, post them up and show us your solutions? That way, we can figure out what the problem is!

Jake

[ssarahj]

Hi everyone, I am just wondering if you guys have any questions for ppm calculations because I sometimes get them wrong in exams. Many thanks Karen.

I'm with you on this Karen, ppm questions are the death of me

[karenc.]

I'm with you on this Karen, ppm questions are the death of me

me too, there were too many questions on this for my trial!

[jakesilove]

me too, there were too many questions on this for my trial!

A good question was from the 2007 HSC Chemistry exam. It tells you that 'Sulfur in diesel is 50 parts per million (ppm)'. Then, it asks you to calculate the volume of sulfur dioxide produced when a full tank (capacity 60 kg) of diesel is consumed. So, how do we approach this question?

We know that parts per million is a weight/weight or v/v measurement. This means that for every gram/kg of a substance, there will be 50 ppm of sulfur in it. So, it's sort of like a percentage! This is the way I think about the question anyway. First, we write ppm as a percentage.



Then, we multiply 60kg by that 'percentage'



Now, we can answer the question! Just combust the Sulfur (using an appropriate chemical formula), figure out the moles of Sulfur dioxide and use the molar volume to find the answer!

Let me know if any of this didn't make sense.

Jake

[RuiAce]

There was a noticeable amount of ppm calculations in James Ruse papers from memory

However, you are much better off posting questions and just asking us to do them if you wish for demonstrations from us. They are tough - probably the second hardest type of calculation in the course.

[karenc.]

A good question was from the 2007 HSC Chemistry exam. It tells you that 'Sulfur in diesel is 50 parts per million (ppm)'. Then, it asks you to calculate the volume of sulfur dioxide produced when a full tank (capacity 60 kg) of diesel is consumed. So, how do we approach this question?

We know that parts per million is a weight/weight or v/v measurement. This means that for every gram/kg of a substance, there will be 50 ppm of sulfur in it. So, it's sort of like a percentage! This is the way I think about the question anyway. First, we write ppm as a percentage.



Then, we multiply 60kg by that 'percentage'



Now, we can answer the question! Just combust the Sulfur (using an appropriate chemical formula), figure out the moles of Sulfur dioxide and use the molar volume to find the answer!

Let me know if any of this didn't make sense.

Jake

Thanks jake your answer made sense Anyways are these formulas correct?  1g=1000mg, 1mg/kg=1mg/L=1ppm

[RuiAce]

Thanks jake your answer made sense Anyways are these formulas correct?  1g=1000mg, 1mg/kg=1mg/L=1ppm

Yes those are correct

[karenc.]

There was a noticeable amount of ppm calculations in James Ruse papers from memory

However, you are much better off posting questions and just asking us to do them if you wish for demonstrations from us. They are tough - probably the second hardest type of calculation in the course.

Thanks for the advice RuiAce I have another question is a raw mark of 85 good enough to get a band 6 when it is scaled?

[jakesilove]

Thanks for the advice RuiAce I have another question is a raw mark of 85 good enough to get a band 6 when it is scaled?

Absolutely! There's no way to figure out how your scaled marks will look, but if you study hard and smash out your HSC, a band 6 is definitely achievable

[RuiAce]

Thanks for the advice RuiAce I have another question is a raw mark of 85 good enough to get a band 6 when it is scaled?

Oh yeah. General trend is that if you're getting at least 85 raw you're safe.

I got a raw mark of 87 and it got aligned up to 93

[conic curve]

Oh yeah. General trend is that if you're getting at least 85 raw you're safe.

I got a raw mark of 87 and it got aligned up to 93

Is raw mark, the internal mark you get in school?

How do you get a raw mark of 90 (I'm trying to aim for 90 but I don't think I'm on that level yet)?

[RuiAce]

Is raw mark, the internal mark you get in school?

How do you get a raw mark of 90 (I'm trying to aim for 90 but I don't think I'm on that level yet)?

I presume she meant her raw mark for the final exam. Not considering internals at all here, only externals.

[jakesilove]

How do you get a raw mark of 90

For every 10 marks, you need to successfully gain 9 of them.

This would require constant study, to the detriment of most of your other subjects, and discipline beyond that of most human beings. I would never be aiming for a raw mark of 90; it's not unachievable, but it's pretty damn tough.

Basically, to get the absolute best atar you can, you need to try consistently hard throughout the year, and do the best you can. Don't aim for a particular mark, except maybe to match/beat your previous mark. You could get raw marks of 60 throughout the year and still get a 99.95 Atar. So don't worry about marks; just try, try and try again.

Jake