CSSA Chemistry Trials (3 Viewers)

[Nuendo]

ok, now.... can someone tell me how hydrogen gets reduced

I put down as my half equation: 2H+ + 2e- --> H2(s)

 

[jet]

HUH? Really? But wasn't it what element underwent beta decay to get thorium? so if thorium was the final product then shouldn't the original element be one less since, as you say, beta decay does go up? I'm confuzzled

You're right.

 

[Shoom]

http://www.boardofstudies.nsw.edu.au/hsc_exams/hsc2008exams/pdf_doc/2008HSC-chemistry.pdf


Q25 , was basically the same as the cell from the CSSA paper, instead of CL gas they used hydrogen for our trial, BOS says the cathode is platinum and that the equation they use for the CL half equation is the same as the one on the data sheet, which is what I did for the trial.

 

[X2RADialbomber]

Some of the questions were quite challenging, but some were good as well. I think that's an okay result for someone whose teacher never teaches us anything. We've done maybe one full prac, and that's it. :mad1:

 

[Nuendo]

http://www.boardofstudies.nsw.edu.au/hsc_exams/hsc2008exams/pdf_doc/2008HSC-chemistry.pdf


Q25 , was basically the same as the cell from the CSSA paper, instead of CL gas they used hydrogen for our trial, BOS says the cathode is platinum and that the equation they use for the CL half equation is the same as the one on the data sheet, which is what I did for the trial.

so does that mean what I put down for the cathode half equation is correct?

 

[ratcher0071]

I put down as my half equation: 2H+ + 2e- --> H2(s)

so does that mean what I put down for the cathode half equation is correct?

According to the table of standard reduction potentials (given in the CSSA exam) you should have put:

H⁺ + e^- --> 1/2 H₂

 

[ratcher0071]

HUH? Really? But wasn't it what element underwent beta decay to get thorium? so if thorium was the final product then shouldn't the original element be one less since, as you say, beta decay does go up? I'm confuzzled

You are right. Thorium was the product. the question was to find which element underwent beta decay to get thorium

 

[team.red14]

at least you didnt miss an entire question....industrial chem last q. just didnt see it

:burn:it was alrite if my bladder didnt give in...I cudnt finish the 6 mk in industrail chem, maybe cos I was busing to go to the loo

sec 1 answers were both weird and easy, MC was screwed..

 

[Nuendo]

According to the table of standard reduction potentials (given in the CSSA exam) you should have put:

H⁺ + e^- --> 1/2 H₂

For the half equation at the anode, I put: Ni(s) --> Ni2+ + 2e- (I think that was the anode, can't remember the question exactly)

I was thinking about putting down what it said on the standard reduction potentials, but then I thought it wouldn't be balanced (since two electrons are being transferred, two must be accepted at the hydrogen end?)

 

[ratcher0071]

sec 1 answers were both weird and easy, MC was screwed..

100% agree with this!

 

[ratcher0071]

For the half equation at the anode, I put: Ni(s) --> Ni2+ + 2e- (I think that was the anode, can't remember the question exactly)

I was thinking about putting down what it said on the standard reduction potentials, but then I thought it wouldn't be balanced (since two electrons are being transferred, two must be accepted at the hydrogen end?)

I thought that too. But I'm not sure exactly how you would put the answer. What you wrote could be right.

 

[DannyT]

pretty sure it was describe i think, not sure, but i did provide with pros and cons for some reason ..... shouldnt have wasted time :-(

and for the electrolytic cell, i am 95% sure it was just hydrogen getting reduced. that was the one of the two tricky questions in the whole exam.

hahah oh man hope so otherwise that's 0 marks for a relatively simple question :/
Also for the ozone monitoring methods did anyone actually describe how the methods worked or just gave examples, gave units its measured in (say DU for TOMS) and kept it brief. 1 marker lolol

the hydrogen getting reduced business, what did everyone put as the two reasons as to why it was unsuitable for a commercial cell?
pissweak voltage? source of hydrogen maybe?

 

[ratcher0071]

hahah oh man hope so otherwise that's 0 marks for a relatively simple question :/
Also for the ozone monitoring methods did anyone actually describe how the methods worked or just gave examples, gave units its measured in (say DU for TOMS) and kept it brief. 1 marker lolol

the hydrogen getting reduced business, what did everyone put as the two reasons as to why it was unsuitable for a commercial cell?
pissweak voltage? source of hydrogen maybe?

For the ozone monitoring methods: I think you should have put how it actually worked.
For the hydrogen/nickel cell: I put the "pissweak voltage" and the source of materials.

 

[jet]

For the hydrogen, I said the voltage, comparing it to a normal dry cell.
My other reason was pretty stupid: "Hydrogen gas is explosive". Lol.

 

[DannyT]

haha i put that at first!
for the ozone monitoring question i didn't explain how one of the methods worked as i thought that 1 mark didn't deserve that....:/ seems more like a 2 marker for that.
the next question had shit wording "outline a step taken to reduce the effect of ozone destroying substances in the stratosphere"
they should've said "outline a step taken to alleviate the problems associated with the use of ozone destroying substances"
You can't do anything about CFCs that are already in the stratosphere they stay there for a while...that's how i saw it.

 

[Nuendo]

For the hydrogen, I said the voltage, comparing it to a normal dry cell.
My other reason was pretty stupid: "Hydrogen gas is explosive". Lol.

I put that down too, and my other reason was that the cell can only produce a voltage at temperatures just above room temperature hahahaa fail. I totally blanked out with that one :mad1:

 

[Shoom]

I said, a eery low voltage and the cost of platinum cathode is to high so its not economically viable.

 

[ally-09]

I said, a eery low voltage and the cost of platinum cathode is to high so its not economically viable.

i said this tooo....

 

[harry4]

for the acid model was it just the same size as it fully dissociated?
for diprotic wouldn't it be double the size for H3O+

 

[ratcher0071]

for the acid model was it just the same size as it fully dissociated?
for diprotic wouldn't it be double the size for H3O+

For a monoprotic acid:
say the height was 2x starting
e.g. HCl --> H⁺ + Cl^-
wouldn't the height of the products be x respectively

For a diprotic acid:
let height be 3x starting
e.g. H₂SO₄ --> 2H⁺ + SO₄^2-
wouldn't height be 2x for H ions and x for SO4 ions