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March 29, 2024, 01:12:29 am

Author Topic: HSC Chemistry Question Thread  (Read 1040565 times)  Share 

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grace_joseph

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Re: Chemistry Question Thread
« Reply #105 on: March 03, 2016, 06:42:46 pm »
+1
Thank you so much Jake! Sorry about being vague, but you have definitely put me on the right track.
Massive help!
Grace :)

William3558

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Re: Chemistry Question Thread
« Reply #106 on: March 03, 2016, 09:15:13 pm »
0
Quick Question, In a back titration with standard sodium hydroxide added in excess to the solution with ammonium... When you boil the solution to evaporate all of the ammonia. Why do you need to keep adding water and keep a constant volume? Is it so the solution doesn't go dry?
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jakesilove

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Re: Chemistry Question Thread
« Reply #107 on: March 03, 2016, 09:32:45 pm »
0
Quick Question, In a back titration with standard sodium hydroxide added in excess to the solution with ammonium... When you boil the solution to evaporate all of the ammonia. Why do you need to keep adding water and keep a constant volume? Is it so the solution doesn't go dry?

Hey William!

I think you are looking for the VCE Question Thread (which is here). We hardly do any of that in the HSC!

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amandali

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Re: Chemistry Question Thread
« Reply #108 on: March 06, 2016, 12:56:48 am »
0
Am i allowed to wrote this condensed ionisation equation for citric acid in hsc exam:
H3X <--> X- + 3H+

and can you check my response thanks:

Compare the environmental sustainability of producing ethanol from petroleum and sugar cane. Support you answer with relevant chemical equations

Petroleum is not environmentally sustainable as it is a non-renewable resource hence will eventually deplete in the future. Moreover, the production of ethanol from petroleum is unsustainable as it involves the process of fractional distillation C6H12O6(aq)--> C6H12O6(l)  and catalytic cracking C4H8(l)-->C2H2(g) + C2H6 (g)which requires enormous amount of energy that are commonly produced by the combustion of fossil fuels which releases CO2 that contributes to global warming.   

In contrast, sugar cane may be sustainable because it can be regrown once harvested thus a renewable resource. However, its production is not completely carbon neutral as petroleum may be combusted to produce energy to operate crop harvesters and trucks which releases more CO2 than it is absorbed to make ethanol.


Happy Physics Land

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Re: Chemistry Question Thread
« Reply #109 on: March 06, 2016, 01:22:50 am »
+3
Am i allowed to wrote this condensed ionisation equation for citric acid in hsc exam:
H3X <--> X- + 3H+

and can you check my response thanks:

Compare the environmental sustainability of producing ethanol from petroleum and sugar cane. Support you answer with relevant chemical equations

Petroleum is not environmentally sustainable as it is a non-renewable resource hence will eventually deplete in the future. Moreover, the production of ethanol from petroleum is unsustainable as it involves the process of fractional distillation C6H12O6(aq)--> C6H12O6(l)  and catalytic cracking C4H8(l)-->C2H2(g) + C2H6 (g)which requires enormous amount of energy that are commonly produced by the combustion of fossil fuels which releases CO2 that contributes to global warming.   

In contrast, sugar cane may be sustainable because it can be regrown once harvested thus a renewable resource. However, its production is not completely carbon neutral as petroleum may be combusted to produce energy to operate crop harvesters and trucks which releases more CO2 than it is absorbed to make ethanol.

Hey Amanda:

Great questions! In regards to your first question, l understand that you would be doing that in order to reduce time consumption. But it is crucial that we dont risk anything in our hsc exams, because you never know who will be marking your essay. Hence it is always good to write the full formula out despite it will cost you several seconds more.

Still referring to your equation, there are some errors that has been made using the condensed formula:
1) After ionisation/donating all the protons, the charge of X wouldnt be X-, but X3-, because citric acid has lost the three protons in its carboxylic bond.
2) The process of ionisation of citric acid is gradual, i.e. it cant be represented in 1 step, because in the chemistry that we learn, the three protons cannot be donated all at once. I.e. it would follow a three-step sequence of: C6H8O7(aq) <---> C6H7O7-(aq) + H(aq), C6H7O7-(aq) <---> C6H6O7(2-)(aq) + H+(aq), C6H6O7(2-)(aq) <---> C6H5O7(3-)(aq) + H+(aq). So yeah this is why I dont recommend the condensed method (unless your teacher reinforce it) because it can yield careless mistakes and it doesnt show the full chemical process.

Referring to your response now, I quite like it because you definitely compared sugar and petroleum to some depth and you've also provided the correct equation of catalytic cracking. If this is a 4 mark question I would definitely give it a 3 and if lm a strict marker l would give it 2. What l recommend you can improve on is to maintain a balance between the amount of pros and cons you give to petroleum and those you give to sugar cane. What you have done there is good, but if we write more on petroleum than sugar cane it would sound a bit biased in terms of your understanding. What you can add to enhance your statement of sugar cane being a environmentally sustainable source is to say "during the cultivation of sugar canes, photosynthesis takes place (provide an equation of photosynthesis) which consumes the carbon dioxide from atmosphere, reducing the amount of greenhouse gas and alleviating global warming". This would make your reasoning stronger for sugar cane. With the equation for fractional distillation, you can include it but that is not the point. A better equation to include is the combustion of ethanol which clearly demonstrates that carbon dioxide is released and it is released a large quantity (2CO2, meaning that for every mole of ethanol combusted, two moles are released).

But Amanda you have been posting a lot of questions on AN which really shows how dedicated you are to your studying. If I sounded a little harsh please dont be discouraged because right now you are doing a super awesome job. If you have any further questions please dont hesitate to ask!

Best Regards
Happy Physics Land
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jakesilove

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Re: Chemistry Question Thread
« Reply #110 on: March 06, 2016, 09:07:43 am »
+1
Am i allowed to wrote this condensed ionisation equation for citric acid in hsc exam:
H3X <--> X- + 3H+

and can you check my response thanks:

Compare the environmental sustainability of producing ethanol from petroleum and sugar cane. Support you answer with relevant chemical equations

Petroleum is not environmentally sustainable as it is a non-renewable resource hence will eventually deplete in the future. Moreover, the production of ethanol from petroleum is unsustainable as it involves the process of fractional distillation C6H12O6(aq)--> C6H12O6(l)  and catalytic cracking C4H8(l)-->C2H2(g) + C2H6 (g)which requires enormous amount of energy that are commonly produced by the combustion of fossil fuels which releases CO2 that contributes to global warming.   

In contrast, sugar cane may be sustainable because it can be regrown once harvested thus a renewable resource. However, its production is not completely carbon neutral as petroleum may be combusted to produce energy to operate crop harvesters and trucks which releases more CO2 than it is absorbed to make ethanol.

I completely agree with HPL's assessment of your answer, and I just have one thing to add. Definitely make sure that you write roughly the same amount for each "half" of the question, and part of that is chemical equations. Make sure to include some sort of chemical equation for the second half. Also, I think it is important to identify that it is biomass (ie. Cellulose) that is important in the production of ethanol from Sugar Cane; it is then easy to claim that this is renewable, as biomass makes up 50% of all plant matter!

Good answer overall though; however I would definitely expand on your second half.

Jake
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lazydreamer

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Re: Chemistry Question Thread
« Reply #111 on: March 06, 2016, 12:42:34 pm »
+1
I'm glad that you find these forums helpful!

I think it really depends on the question itself. For an ethanol question, a table with advantages and disadvantages always works best. You will always tailor it for what sort of question it is (are there two clear sides to the argument, and so can you use a table? Are there multiple important components (eg. for your Battery) and so can you use subheadings?).

The important part is that you actually explain WHY an aspect is good/bad etc. It is not enough to say Ethanol has a lower molar heat of combustion: Explain how this has a negative impact on consumers.

Also, make sure you address EACH COMPONENT of the question. It is really easy to skip a word in a question that ends up being 3 marks worth of content. Underline the important part of the question, and address everything.

I don't think that there is a set structure. For an assess/evaluate, you will almost always have advantages/disadvantages, so I think a table/subheadings is always appropriate. However I think the best way to make sure you are prepared for extended response question is to do one standard question from each topic, re write it until it is perfect (marked by us or your teachers) and then put it in your notes.

Good luck!

Jake

hello, sorry it was an oldish post but a question about using tables...
Could i get away with incorporating tables for questions like assess, compare/contrast, discuss etc? it's so much easier to organise information that way and looks better than a huge chunk of words, would markers appreciate that or...nah? haha
aaand because i don't have time to write a detailed paragraph

thanks

Happy Physics Land

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Re: Chemistry Question Thread
« Reply #112 on: March 06, 2016, 01:00:52 pm »
0
hello, sorry it was an oldish post but a question about using tables...
Could i get away with incorporating tables for questions like assess, compare/contrast, discuss etc? it's so much easier to organise information that way and looks better than a huge chunk of words, would markers appreciate that or...nah? haha
aaand because i don't have time to write a detailed paragraph

thanks

Hey LazyDreamer:

Definitely yes for compare and contrast. If you use a table for compare and contrast and include the suitable information and suitable titles, then its almost a guaranteed full mark. Cautions needs to be taken with questions that involve evaluate, discuss or assess. These questions require a logical flowing response, i.e. you need to use linking words. Even if you are using a table for these questions, you would still need linking words and words that show cause and effect. If you are using a table for evaluate a assess, you must also make two clear judgments in your response in order to secure full marks. But yes, generally saying, a table is a great way to reduce time consumption whilst still effective presenting your response to the question.

Best Regards
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lazydreamer

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Re: Chemistry Question Thread
« Reply #113 on: March 06, 2016, 01:29:55 pm »
0
Hey LazyDreamer:

Definitely yes for compare and contrast. If you use a table for compare and contrast and include the suitable information and suitable titles, then its almost a guaranteed full mark. Cautions needs to be taken with questions that involve evaluate, discuss or assess. These questions require a logical flowing response, i.e. you need to use linking words. Even if you are using a table for these questions, you would still need linking words and words that show cause and effect. If you are using a table for evaluate a assess, you must also make two clear judgments in your response in order to secure full marks. But yes, generally saying, a table is a great way to reduce time consumption whilst still effective presenting your response to the question.

Best Regards
Happy Physics Land

thanks for answering, i'll keep that in mind for pre-trials and see how i go :)
and i agree that for evaluate/discuss/assess qns i would need to include a couple of sentences at the end that makes a judgement. As for linking cause and effect, couldn't that be included in the table, eg |Cause|Effect|Evaluation|

btw
Quote
If you are using a table for evaluate a assess, you must also make two clear judgments in your response in order to secure full marks.
what do you mean by 2 clear judgments?

Happy Physics Land

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Re: Chemistry Question Thread
« Reply #114 on: March 06, 2016, 01:38:47 pm »
+1
thanks for answering, i'll keep that in mind for pre-trials and see how i go :)
and i agree that for evaluate/discuss/assess qns i would need to include a couple of sentences at the end that makes a judgement. As for linking cause and effect, couldn't that be included in the table, eg |Cause|Effect|Evaluation|

btw what do you mean by 2 clear judgments?

Ok so this might sound a little dumb but for example if you are asked to assess the impact of polyethylene on the society, in your first dotpoint/establishing sentence, you must state that polyethylene has had a significant/mediocre/insignificant impact upon the society (making a judge). At the end of your answer, l would literally write "Final Judgement: Polyethylene has had a tremendous impact upon the society". You can just include one judgment if you want, but for me, having a judgment at the start and having another one in the end helps to make your statements sound stronger.
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lazydreamer

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Re: Chemistry Question Thread
« Reply #115 on: March 06, 2016, 02:14:21 pm »
+1
Ok so this might sound a little dumb but for example if you are asked to assess the impact of polyethylene on the society, in your first dotpoint/establishing sentence, you must state that polyethylene has had a significant/mediocre/insignificant impact upon the society (making a judge). At the end of your answer, l would literally write "Final Judgement: Polyethylene has had a tremendous impact upon the society". You can just include one judgment if you want, but for me, having a judgment at the start and having another one in the end helps to make your statements sound stronger.

not at all  ;D reads like an essay paragraph to me:  thesis statement that answers the qn, then supporting points, then a link back to the question. Makes sense i guess, thanks!

jakesilove

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Re: Chemistry Question Thread
« Reply #116 on: March 06, 2016, 03:11:42 pm »
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not at all  ;D reads like an essay paragraph to me:  thesis statement that answers the qn, then supporting points, then a link back to the question. Makes sense i guess, thanks!

Just wanted to back up HPL here: Totally agree with what he's said! If you have any further questions, about this or anything else, please don't hesitate to post :)

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Re: Chemistry Question Thread
« Reply #117 on: March 06, 2016, 03:32:26 pm »
+4
Just wanted to back up HPL here: Totally agree with what he's said! If you have any further questions, about this or anything else, please don't hesitate to post :)

Jake

this site is great, much easier to get help than on BoS (which is blocked on the school laptops lol) so when i found a forum which was actually unblocked with a helpful community, it felt like i died and went to hsc heaven. Thanks, i think i'll be using this consistently throughout the year :)

Happy Physics Land

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Re: Chemistry Question Thread
« Reply #118 on: March 06, 2016, 07:18:14 pm »
0
this site is great, much easier to get help than on BoS (which is blocked on the school laptops lol) so when i found a forum which was actually unblocked with a helpful community, it felt like i died and went to hsc heaven. Thanks, i think i'll be using this consistently throughout the year :)

Hahaha its good to know that we are helping you lazydreamer!!! Your involvement will make our community an even greater place than it was! :D

Happy Posting!

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RuiAce

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Re: Chemistry Question Thread
« Reply #119 on: March 07, 2016, 10:27:28 am »
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Ok so this might sound a little dumb but for example if you are asked to assess the impact of polyethylene on the society, in your first dotpoint/establishing sentence, you must state that polyethylene has had a significant/mediocre/insignificant impact upon the society (making a judge). At the end of your answer, l would literally write "Final Judgement: Polyethylene has had a tremendous impact upon the society". You can just include one judgment if you want, but for me, having a judgment at the start and having another one in the end helps to make your statements sound stronger.
Will add my 2 cents to this.

To be honest, I reckon when giving the evaluation a good evaluation could be something such as

Polyethylene has benefited society appreciably through it's wide ranges of applications (give reasoning) however further improvements could still be made in shifting away from these resources and using biopolymer alternatives.

(Usually evaluate questions at this time of the year seem to be ethanol though so I would say overall, it is the renewability of the resource that ultimately makes ethanol a viable alternate fuel source.)

(Do forgive me though - I'm sleep-deprived right now so I don't feel like reading too much of what I missed.)