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HSC 2012-2015 Chemistry Marathon (archive) (7 Viewers)

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someth1ng

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re: HSC Chemistry Marathon Archive

Don't think you can assume something like that in a question like this, past HSC calculation questions for these cells usually provides labelled diagrams of the cells in use. The salt bridge could contain any inert salt like NaCl/KCl or some other salt depending on the contents of the half cells, even though a NO3- based one would probably be best suited for this scenario.

Someone should attempt the question though.
It's fine to assume that as long as you don't write it down. A better way of putting it is to assume that the salt bridge electrolyte does not react with the half cell electrolytes.
 

Librah

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re: HSC Chemistry Marathon Archive

It's fine to assume that as long as you don't write it down. A better way of putting it is to assume that the salt bridge electrolyte does not react with the half cell electrolytes.
His question required it specifically to be some kind of NO3- based electrolyte in the salt bridge though. So it kind of needs to be stated/written down in brackets (assume NO3- is in the salt bridge), or atleast give an indication of how the nitrate concentration would increase.
 
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Drsoccerball

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re: HSC Chemistry Marathon Archive

Explain with the aid of chemical equations, why sydney rain is usually more acidic than rain in the blue mountains. 3 Marks
 

curiouscat98

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re: HSC Chemistry Marathon Archive

(Bump) Could someone please answer the above question about acid rain? - my teacher hasn't even touched that dot point and we're having a test on it next week (yes, my teacher is a genius *clapclapclap*)
 

Drsoccerball

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(Bump) Could someone please answer the above question about acid rain? - my teacher hasn't even touched that dot point and we're having a test on it next week (yes, my teacher is a genius *clapclapclap*)
Give your teacher a pat on the back :)
*Insert explanation of acid rain*Sydney is a more industrialized area so there are more cars, factories,ect... These produce carbon dioxide and this carbon dioxide mixes to form carbonic acid. At the blue mountains there isn't as much pollution as there is in sydney. This question requires geography to some extent i do not know. For example if there were mines in blue mountains, factories, volcanoes that would also contribute:)
 

Librah

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Give your teacher a pat on the back :)
*Insert explanation of acid rain*Sydney is a more industrialized area so there are more cars, factories,ect... These produce carbon dioxide and this carbon dioxide mixes to form carbonic acid. At the blue mountains there isn't as much pollution as there is in sydney. This question requires geography to some extent i do not know. For example if there were mines in blue mountains, factories, volcanoes that would also contribute:)
Sulfur/nitrogen oxides?
 

Drsoccerball

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re: HSC Chemistry Marathon Archive

Am i the only one that finished acidic environment? Next question:
What are some environmental effects of acid rain? Include a relevant chemical equation. 4 marks
 

someth1ng

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re: HSC Chemistry Marathon Archive

Might be a bit advanced but...

Explain why low density polyethylene is more transparent than high density polyethylene.
 

Librah

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i mentioned about volcanoes right?..
There aren't any volcano's in the Blue Mountains, and even if there were, there would be no real purpose of your question, since you'd be giving reasons for why it may be more acidic in the blue mountains, unless your trying to say there's a volcano in the middle of Sydney, even then it's a natural source of sulfur and not really relevant.

Also acid rain is almost always acidic due to carbonic acid, so more CO2 won't have much greater of an effect. When they say "acid rain" they're referring to the much stronger acids formed like sulfurous acid/nitrous acid and some of the "strong" acids, that will actually have a noticeable effect in the city. So you mention the sources of SO2 from industry, like from burning of pyrite containing coal or smelting. Then show how it forms acid rain with many chemical eqs.
 
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siggy

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re: HSC Chemistry Marathon Archive

Might be a bit advanced but...

Explain why low density polyethylene is more transparent than high density polyethylene.
LDPE is more transparent due to its' branching structure as a result of the high-pressure method of producing polyethylene. HDPE on the otherhand is produced via the ziegler-natta process which results in unbranched chains of polyethylene. Hence, LDPE is more transparent due to its' larger room for holes between the branching, whereas HDPE is very dense and so is far less transparent than LDPE.
 

Drsoccerball

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can someone explain to me the use of the dotpoint: process info from secondary sources to determine recent discoveries of elements... and give a question on it?
 

Kaido

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Yeah that's just the production of elements such as curium etc. (particle accelerator generated elements)
new prob means last 50 years, lol
 

someth1ng

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re: HSC Chemistry Marathon Archive

LDPE is more transparent due to its' branching structure as a result of the high-pressure method of producing polyethylene. HDPE on the otherhand is produced via the ziegler-natta process which results in unbranched chains of polyethylene. Hence, LDPE is more transparent due to its' larger room for holes between the branching, whereas HDPE is very dense and so is far less transparent than LDPE.
Doesn't really address the issue because density of HDPE and LDPE are almost identical so you'd expect a similar amount of those holes that you talked about.
 

siggy

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Doesn't really address the issue because density of HDPE and LDPE are almost identical so you'd expect a similar amount of those holes that you talked about.
Really? Oh I dunno if it's not the density, I thought that was the whole point
 

Loudvicuna

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Doesn't really address the issue because density of HDPE and LDPE are almost identical so you'd expect a similar amount of those holes that you talked about.
Really? why is one called low density and the other high density then? Surely the name indicates a significant difference in the density of both polymers. L.D.P.E is a branched structure which is less dense allowing more transparency then the high density linear structure of H.D.P.E which is more "compact" thus less transparency
 

Kaido

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re: HSC Chemistry Marathon Archive

From ideas to imp (i think), i believe transparency has to do with the crystalline structure of the polyethylene. The lower density and non-uniform branching structure equates to less crystalline regions that enable light to pass through -> thus more transparent?
 

Drsoccerball

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re: HSC Chemistry Marathon Archive

From ideas to imp (i think), i believe transparency has to do with the crystalline structure of the polyethylene. The lower density and non-uniform branching structure equates to less crystalline regions that enable light to pass through -> thus more transparent?
Wrong forum dude
 

Librah

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Really? why is one called low density and the other high density then? Surely the name indicates a significant difference in the density of both polymers. L.D.P.E is a branched structure which is less dense allowing more transparency then the high density linear structure of H.D.P.E which is more "compact" thus less transparency
The density of HDPE is actually only slightly higher than LDPE.

From ideas to imp (i think), i believe transparency has to do with the crystalline structure of the polyethylene.
It's got to do with the crystalline structure yes.

This is more of a physics question, for Q2Q/ideas to impentation.
 
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Crisium

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re: HSC Chemistry Marathon Archive

I came across what constitutes how crystalline or how amorphous LDPE / HDPE is from a few textbooks
 
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