HSC 2012-2015 Chemistry Marathon (archive) (4 Viewers)

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leehuan

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re: HSC Chemistry Marathon Archive

like 3 or 4 out of 7, but im not sure if it was just because laziness.

Read my answer above for a better response.
When this question was asked, only TWO applications described to reasonable detail was required. 3-4 is a bit harshly marked. I would say 5 because the question has been addressed, just not to a substantial depth. Obviously your response is a 7 but in the exam there's definitely not enough room to write all of that. It's like me when I answer some questions on here.
 
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leehuan

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re: HSC Chemistry Marathon Archive

New Question:

Name all the elements in the Periodic Table in alphabetical order.

(7 marks)
I actually cared to memorise the periodic table when I was in Year 10 in atomic number order. This question is so troll though Speed; you get a periodic table in the exam!
 

keepLooking

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I actually cared to memorise the periodic table when I was in Year 10 in atomic number order. This question is so troll though Speed; you get a periodic table in the exam!
They will use this to differentiate between a Band 6 student and a Band 5 student. ;D
 

leehuan

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re: HSC Chemistry Marathon Archive

I don't believe it. How do we know that you didn't have your phone open with the periodic table on it.
Do you want me to turn on the webcam next time I record it?

I'll also record my table in it.
 
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Ekman

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Do you want me to turn on the webcam next time I record it?
Yes with audio as well. How do we know that someone wasn't behind you saying the elements one by one
 

leehuan

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Yes with audio as well. How do we know that someone wasn't behind you saying the elements one by one
Sure. I'll do that later when I'm in the library otherwise you could still call me cheating for memory recall.
 

Mr_Kap

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When this question was asked, only TWO applications described to reasonable detail was required. 3-4 is a bit harshly marked. I would say 5 because the question has been addressed, just not to a substantial depth. Obviously your response is a 7 but in the exam there's definitely not enough room to write all of that. It's like me when I answer some questions on here.
i wrote that response in m half yearly...teacher put this question in. (obiously i didn't mention like VLDPE, CPE, and all those others...i was just trolling now).

Its just that he did it in bullet points, but yeh. Also, realised he answered the question that Mufasa put up, I answered the HSC 2006 question (slightly different to the one mufasa put up), which was to assess the statement, so i didn't see an assessment in his thats why i thought like a 4.
 

leehuan

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re: HSC Chemistry Marathon Archive

i wrote that response in m half yearly...teacher put this question in. (obiously i didn't mention like VLDPE, CPE, and all those others...i was just trolling now).

Its just that he did it in bullet points, but yeh. Also, realised he answered the question that Mufasa put up, I answered the HSC 2006 question (slightly different to the one mufasa put up), which was to assess the statement, so i didn't see an assessment in his thats why i thought like a 4.
This is science. The HSC is more generous than you think; people get band 6's doing bullet points in the science courses with enough sophistication


Sent from my iPhone using Tapatalk
 

Mufasa64

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i wrote that response in m half yearly...teacher put this question in. (obiously i didn't mention like VLDPE, CPE, and all those others...i was just trolling now).

Its just that he did it in bullet points, but yeh. Also, realised he answered the question that Mufasa put up, I answered the HSC 2006 question (slightly different to the one mufasa put up), which was to assess the statement, so i didn't see an assessment in his thats why i thought like a 4.

Tbh Kap your answer about ethanol not being viable for use as a fuel from ethylene is debatable. It's currently being used as a petrol extender up to 10% in Australia that's why the petrol you use is called E10 unleaded and in countries such as Brazil some cars use 100% ethanol. It's good to say it's not viable from use from ethylene rather fermenting glucose which is good and that's what you said but I reckon it wouldn't be good to have such a strong opinion, it can be made from ethylene and remember that fermenting glucose from biomass also uses considerable energy derived from petroleum. But otherwise your answer is really good 6/7 just for the above and for not talking about it as a solvent.
 

Khan.Paki

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re: HSC Chemistry Marathon Archive

Next Question:

1) Justify the continued use of the Arrhenius definition of acids and bases, despite the development of the more sophisticated Brönsted–Lowry definition. [3 marks]

2) Why does the neutralisation of any strong acid in an aqueous solution by any strong base always result in a heat of reaction of approximately –57 kJ mol? [1 mark]
 

leehuan

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re: HSC Chemistry Marathon Archive

Next Question:

1) Justify the continued use of the Arrhenius definition of acids and bases, despite the development of the more sophisticated Brönsted–Lowry definition. [3 marks]

2) Why does the neutralisation of any strong acid in an aqueous solution by any strong base always result in a heat of reaction of approximately –57 kJ mol? [1 mark]
1) Through the Arrhenius definition of acids and bases many principles of the behaviour of these chemicals were understood. (It defined acids as substances that ionised in water to produce H+, and bases as those that produced OH- similarly.) The degree of ionisation of an acid was used to distinguish between strong and weak acids, and similarly for base. It also formed the basis of the development of the pH scale. Arrhenius also explained the neutralisation of acids and bases, to which we now understand as [Acid + Base -> Salt + Water]. This theory interpreted the behaviour of acids and bases to a much more significant extent than previous theories, and was only flawed in it's inability to explain the acidic nature of oxides and other bases such as Na2CO3, thus it is still suitable to explain the acidic/basic nature of a variety of substances. (It can also be taught as a simplified model of B-L theory.)

2) The reaction between a strong acid and a strong base involves the reaction of essentially all H+ and OH- ions, due to the fact that the acid and base are (technically assumed to be) fully ionised. For every mole of H+ reacted with a mole of OH-, the enthalpy is -57kJ, thus this neutralisation will produce a heat of reaction of -57kJmol^-1 always.
___________________________________________________
NEXT QUESTION:
Justify the methods of treating acid spills in the laboratory and compare it to those at the industrial level. (4)
 
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Mr_Kap

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Tbh Kap your answer about ethanol not being viable for use as a fuel from ethylene is debatable. It's currently being used as a petrol extender up to 10% in Australia that's why the petrol you use is called E10 unleaded and in countries such as Brazil some cars use 100% ethanol. It's good to say it's not viable from use from ethylene rather fermenting glucose which is good and that's what you said but I reckon it wouldn't be good to have such a strong opinion, it can be made from ethylene and remember that fermenting glucose from biomass also uses considerable energy derived from petroleum. But otherwise your answer is really good 6/7 just for the above and for not talking about it as a solvent.
I mentioned it was an industrial solvent. And this questions was 'faulty' per say, as ethanol is the only fuel that can be made from ethylene, but they dont use ethylene to make ethanol in fuels. If they are gonna make ethanol for fuel they do it from sugar cane. Check what roland smith has to say about this question..i agree with him fully. And why the fuck would you use ethylene to make ethanol to use as a fuel, when you can use octane etc. The only reason we are trying to use ethanol in the first place is because it can be obtained from renewable sources, and is also greenhouse neutral (when considering the CO2 from photosynthesis + fermentation = CO2 from combustion.) But if we produce it from ethylene, which is obtained from a non renewable source, then what is actually the point. We are not solving any environmental issues (maybe the fact that incomplete combustion is less likely to occur but still), and ethanol's molar heat of combustion is less than octane, and other fuels, yeh.
 
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Mr_Kap

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re: HSC Chemistry Marathon Archive

Next Question:

1) Justify the continued use of the Arrhenius definition of acids and bases, despite the development of the more sophisticated Brönsted–Lowry definition. [3 marks]

2) Why does the neutralisation of any strong acid in an aqueous solution by any strong base always result in a heat of reaction of approximately –57 kJ mol? [1 mark]
2) Because they all have the same proton transfer eqn of H+ + OH- ---> H2O

Proton has been transferred from the acid to the base to form H2O.
 

amberbambi

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re: HSC Chemistry Marathon Archive

Outline a method used to measure the sulphate content of a lawn fertiliser.
 

moonshoes

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re: HSC Chemistry Marathon Archive

I'm doing 2007 Chemistry from the purple Excel book. In Industrial Chemistry Q28 c) calculating K.JPG

But the answer in the Excel book doesn't regard 3 moles of Sulfur when calculating K so all it is is [H20]^2/ [H2s]^2 x [SO2]. Isn't that wrong? I included 3S in my calculation of K and ended up getting K = 1.69 @ 373 K for ii)

Help please :D
 

Mr_Kap

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re: HSC Chemistry Marathon Archive

I'm doing 2007 Chemistry from the purple Excel book. In Industrial Chemistry Q28 c) View attachment 32552

But the answer in the Excel book doesn't regard 3 moles of Sulfur when calculating K so all it is is [H20]^2/ [H2s]^2 x [SO2]. Isn't that wrong? I included 3S in my calculation of K and ended up getting K = 1.69 @ 373 K for ii)

Help please :D
equillibrium constant not affected by solids. Sulfur is a solid here. Excel is right
 
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