Predictions for Chemistry 2014 HSC? (7 Viewers)

[photastic]

Don't get me wrong, I'm shit, I just enjoy it haha

Modesty/10

 

[SuchSmallHands]

Modesty/10

Realism/10

 

[faisalabdul16]

Hoping for 94+. How hard is it to get 96?

Once you're in the band 6 range, getting extra HSC marks (i.e, 91,92 etc) progressively get harder, requiring more raw marks. 96 is a mark close to state rank, so I'm guessing 90 raw.

What's back titration

titration backwards

Teach me how to be interested in chemistry 98+ atar

You teach us.

Don't get me wrong, I'm shit, I just enjoy it haha

Humble/10

Modesty/10

Yes he is modest.

Realism/10

Bullshitism/10

 

[photastic]

Once you're in the band 6 range, getting extra HSC marks (i.e, 91,92 etc) progressively get harder, requiring more raw marks. 96 is a mark close to state rank, so I'm guessing 90 raw.

titration backwards

You teach us.

Humble/10

Yes he is modest.

Bullshitism/10

Isn't SSH a she?

 

[QZP]

Yes and she goes to some rural school and is rank 1st in everything and achieved dux

 

[SuchSmallHands]

Isn't SSH a she?

I had believed so

 

[SuchSmallHands]

Yes and she goes to some rural school and is rank 1st in everything and achieved dux

Hey, we don't have our ATARs yet, don't want to call dux early (srs how do you know these things?)

 

[QZP]

I meticulously read all 534 posts of yours and took down notes. /Realism

 

[SuchSmallHands]

I meticulously read all 534 posts of yours and took down notes.

Topping the state in SSH studies.

 

[faisalabdul16]

Isn't SSH a she?

It's 1 a.m.
That's my excuse.
Soz

Topping the state in SSH studies.

hahaha

 

[SuchSmallHands]

back on topics other than me:

Analyse how knowledge of the composition and properties of acids has led to changes in the definition of acids. (5 marks)

 

[photastic]

back on topics other than me:

Analyse how knowledge of the composition and properties of acids has led to changes in the definition of acids. (5 marks)

Antoine Lavoisier was one of the first chemists to propose a theory that attempted to define an acid based on its composition rather than its properties. Following experimental observations that non- metal oxides such as CO2 could dissolve in water to produce solutions with the characteristic properties of acids (such as sour taste and turning blue litmus red), Lavoisier proposed that acids were substances containing oxygen. This theory, however, was problematic, as it was recognised that some oxygen-containing substances like metal oxides were actually basic, and some distinctly acidic substances such as HCl, in fact contained no oxygen.

This theory, although unsatisyfing, drew attention to the task of defining acids by their composition, paving the way for Humphry Davy to propose a new theory, that acids were substances containing hydrogen. This was supported by Davy’s demonstration that hydrogen gas was produced upon electrolysis of acid solutions. Again however, there were problems with this theory, as substances like methane (CH4) were clearly not acidic despite containing abundant hydrogen. Moreover, Davy’s simplistic theory still failed to adequately account for various other properties of acids, such as the ability to neutralise bases.

Drawing from his pioneering work on ions as charge carriers in solution and the observation that acid solutions were electrolytes, Savante Arrhenius was able to refine Davy’s definition, proposing that acids were substances that ionised to produce hydrogen ions (H+) in aqueous solution. This theory represented a great leap forward in the understanding of acids, as it distinguished strong and weak acids in terms of degree of ionisation, and was able to explain neutralisation as reactions of H+ from acids and OH– ions from bases. This theory is still utilised today, although it has been superseded by the more general Bronsted-Lowry theory, which defines acids as proton donors and is able to explain the behaviour of acids in non-aqueous solvents.

 

[faisalabdul16]

Antoine Lavoisier was one of the first chemists to propose a theory that attempted to define an acid based on its composition rather than its properties. Following experimental observations that non- metal oxides such as CO2 could dissolve in water to produce solutions with the characteristic properties of acids (such as sour taste and turning blue litmus red), Lavoisier proposed that acids were substances containing oxygen. This theory, however, was problematic, as it was recognised that some oxygen-containing substances like metal oxides were actually basic, and some distinctly acidic substances such as HCl, in fact contained no oxygen.

This theory, although unsatisyfing, drew attention to the task of defining acids by their composition, paving the way for Humphry Davy to propose a new theory, that acids were substances containing hydrogen. This was supported by Davy’s demonstration that hydrogen gas was produced upon electrolysis of acid solutions. Again however, there were problems with this theory, as substances like methane (CH4) were clearly not acidic despite containing abundant hydrogen. Moreover, Davy’s simplistic theory still failed to adequately account for various other properties of acids, such as the ability to neutralise bases.

Drawing from his pioneering work on ions as charge carriers in solution and the observation that acid solutions were electrolytes, Savante Arrhenius was able to refine Davy’s definition, proposing that acids were substances that ionised to produce hydrogen ions (H+) in aqueous solution. This theory represented a great leap forward in the understanding of acids, as it distinguished strong and weak acids in terms of degree of ionisation, and was able to explain neutralisation as reactions of H+ from acids and OH– ions from bases. This theory is still utilised today, although it has been superseded by the more general Bronsted-Lowry theory, which defines acids as proton donors and is able to explain the behaviour of acids in non-aqueous solvents.

so long Ceebs reading it all hahahah

 

[mreditor16]

Looks good actually but I think you could make it more concise, handwritten that would be too long and its lots of unnecessary depth. But very thorough knowledge!

Haha Faisalabdul I'll be happy with 92+ in chem. My internal ranks not great but that was mainly because I majorly screwed up a prac exam worth heaps, but my half yearly and trials were decent so I'm hoping that if I achieve similar external marks I can make it

Omg suchsmallhands you do chem of art too YAY!

Yes next question. Dicuss the implications of the use of radioisotopes in medicine (5 marks)

but our chem cohort is so strong. so dw too much. btw will reply to your PM soon.

 

[enigma_1]

There has been an increase in the concentration of the oxides of nitrogen, sulphur and CO2 in the atmosphere as a result of combustion.
Assess both the evidence to support this statement and the need to monitor these oxides. (5 marks)

(I'm gonna tweak the question a bit and include all the oxides, but I don't think they'll specify like that in the question coz they always ask for all of them usually)

This would take 2 seconds, show both reactions which form via combustion: S(s) + O2(g) --> SO2(g) and
N2(g) + O2(g) -->2NO(g) then 2NO(g) + O2(g) --> NO2(g)

1) Direct evidence: quantitative analysis of Antarctic ice core samples by CSIRO hav shown steady increases in concentrations of these oxides. The process requires drilling holes into these ice core samples and analysing the different concentrations of these oxides, where the latest results are obtained at the top of the sample and the oldest are at the bottom. Thus, if in the Antarctic, the concentrations of these oxides are increasing (where there is not much pollution by humans), then it can be inferred that the concentration of these oxides would be increasing at a greater rate in urban areas.
Limitation of this method: the sensitive gas analytical techniques used to measure very low concentrations of these oxides were only recently developed in the 1970s, so there is not a wide enough time span to adequately determine a trend. Furthermore, oxide levels were difficult to measure below 0.01ppm. Also, SO2 and NOx are highly soluble because of the sulfate and nitrate ions which are soluble, and thus dissolve in oceans, so the atmospheric concentration may only really be a fraction of the total concentration of these oxides released into the atmosphere.

2) Indirect evidence: qualitative analysis of the increasing incidence of acid rain corroding metal and limestone structures:
This is occurring more and more often than before, along with the increasing incidence of pollution and photochemical smog, thus indicative of increasing concentrations of these oxides.
Limitations of this method: this method is qualititative and is not as accurate as the quantitative method.

Now, the need to monitor these oxides concentrations:

1) Formation of acid rain which can destroy entire forests, corrode limestone structures:
CaCo3(s) + H2SO4(aq) --> CaSO4(aq) + CO2(g) + H20(l) where the CaSO4 is soluble and is washed away.
And also, acid rain corroding metal structures:
H2S04(aq) + Fe(s) -->FeSO4(aq) + H2(g)
Acid rain also distorts the pH levels in water bodies.

2) Health problems:
- CO2 does not have any
- CO is a serious respiratory irritant as it binds to haemoglobin faster than oxygen, preventing oxygen intake in the lungs.
- SO2 aggravates asthma
- NOx irritates the eyes, but this is not its greatest concern

3) NOx leads to the formation of photochemical smog when it is exposed to UV light (brown green layer). The main problem with this is that it facilitates the formation of ozone which is a serious respiratory irritant.
NO2(g) ----UV Light----> NO(g) + O. (g)
O.(g) + O2(g) --> O3(g)

Ozone is also toxic. It corrodes metaL and plastic structures.

ASSESSMENT: Due to these problems, the concentrations of these oxides need to be monitored in order to reduce their effects on man-made structures and humans. Although current analytical techniques may not be accurate, future research may be able to develop better techniques to analyse the concentrations of these oxides.

(That is probably more than what you need for a 5 marker, but depending on the wording of the question, you would use more or less of each section in your answer)

 

[faisalabdul16]

but our chem cohort is so strong. so dw too much. btw will reply to your PM soon.

Every cohort in your school is strong. -.-

Discuss the implications of the use of radioisotopes in medicine (5 marks)

The use of radioisotopes in the nuclear medical field have proven to not only have significant advantages but also disadvantages which must be overcome in order to ensure the safety of individuals. Technetium 99m is a radioactive tracer isotope used in the nuclear medical field for diagnostic imaging where small amounts are injected into the patients body, and it's movement monitored through a scintillation camera, giving a clear indication of its position on the body. Technetium 99m has been advantagous due to its use in detecting blood clots, circulation, disorders and brain tumours. The use of technetium 99m is advantagous and used widely because of it's physical and chemical properties. The 'm' in "99m" means metable state, ensuring that technetium 99m will not transform into any other substance in the body. It is a gamma emitter so low energy rays pass out and has a half life of 6 hours, reducing the amount of the substance in the human body fairly quickly. It can also attach itself to biological carriers and target specific body organs. Can be combined chemically with tin in the Red Blood Cells and map out specific areas of circulatory system disorders and brain tumours. However, despite the numerous advantages, there is some concerning factors such as the fact that radiation is entering the body. It is vital to ensure that technetium 99m is injected into the correct area which is being 'inspected' to reduce the amount of exposure to radiation as possible because radiation can potentially alter the genetic make up of individuals, leading to the production of modified proteins and enzymes, possibly resulting in malfunctioning of metabolic activity. Furthermore, the use of stronger compounds such as Cobalt-60 in the medical field have benefits associated with its properties and use, however has implications which need to be dealt with care. Cobalt-6O is used to kill cancerous cells, and due it's ability to penetrate metal and being a gamma emitter, it is vital that doctors target specific cancerous cells and kill them only, as killing other normal cells could potentially as stated previously result in decreased enzyme activity and metabolic efficiency. Moreover, patients who are pregnant are NOT able to receive treatment from Cobalt-60 as it could potentially kill the unborn baby, and patients who have been in contact must be isolated from members of the community and their family, to avoid the spread of radiation. This is an implication as individuals are unable to work or make contact with family members. Thereby, compounds such as technetium-99m and Cobalt 60 have proven to have numerous benefits to the community, however serious implications do arise which must be dealt with care and close awareness to prevent any mishaps.

 

[faisalabdul16]

(I'm gonna tweak the question a bit and include all the oxides, but I don't think they'll specify like that in the question coz they always ask for all of them usually)

This would take 2 seconds, show both reactions which form via combustion: S(s) + O2(g) --> SO2(g) and
N2(g) + O2(g) -->2NO(g) then 2NO(g) + O2(g) --> NO2(g)

1) Direct evidence: quantitative analysis of Antarctic ice core samples by CSIRO hav shown steady increases in concentrations of these oxides. The process requires drilling holes into these ice core samples and analysing the different concentrations of these oxides, where the latest results are obtained at the top of the sample and the oldest are at the bottom. Thus, if in the Antarctic, the concentrations of these oxides are increasing (where there is not much pollution by humans), then it can be inferred that the concentration of these oxides would be increasing at a greater rate in urban areas.
Limitation of this method: the sensitive gas analytical techniques used to measure very low concentrations of these oxides were only recently developed in the 1970s, so there is not a wide enough time span to adequately determine a trend. Furthermore, oxide levels were difficult to measure below 0.01ppm. Also, SO2 and NOx are highly soluble because of the sulfate and nitrate ions which are soluble, and thus dissolve in oceans, so the atmospheric concentration may only really be a fraction of the total concentration of these oxides released into the atmosphere.

2) Indirect evidence: qualitative analysis of the increasing incidence of acid rain corroding metal and limestone structures:
This is occurring more and more often than before, along with the increasing incidence of pollution and photochemical smog, thus indicative of increasing concentrations of these oxides.
Limitations of this method: this method is qualititative and is not as accurate as the quantitative method.

Now, the need to monitor these oxides concentrations:

1) Formation of acid rain which can destroy entire forests, corrode limestone structures:
CaCo3(s) + H2SO4(aq) --> CaSO4(aq) + CO2(g) + H20(l) where the CaSO4 is soluble and is washed away.
And also, acid rain corroding metal structures:
H2S04(aq) + Fe(s) -->FeSO4(aq) + H2(g)
Acid rain also distorts the pH levels in water bodies.

2) Health problems:
- CO2 does not have any
- CO is a serious respiratory irritant as it binds to haemoglobin faster than oxygen, preventing oxygen intake in the lungs.
- SO2 aggravates asthma
- NOx irritates the eyes, but this is not its greatest concern

3) NOx leads to the formation of photochemical smog when it is exposed to UV light (brown green layer). The main problem with this is that it facilitates the formation of ozone which is a serious respiratory irritant.
NO2(g) ----UV Light----> NO(g) + O. (g)
O.(g) + O2(g) --> O3(g)

Ozone is also toxic. It corrodes metaL and plastic structures.

ASSESSMENT: Due to these problems, the concentrations of these oxides need to be monitored in order to reduce their effects on man-made structures and humans. Although current analytical techniques may not be accurate, future research may be able to develop better techniques to analyse the concentrations of these oxides.

(That is probably more than what you need for a 5 marker, but depending on the wording of the question, you would use more or less of each section in your answer)

Just elaborate on the effects a little more.
Do not see any problems with it. I'd give it a 5/5

 

[faisalabdul16]

LOL not every cohort. Personal opinion but I think our 2u maths and English cohorts aren't too great in comparison to previous years, but will demolish any other school in regards to number of band 6's... :/

Dude this is like a model answer. I want to like frame it or something hahaha, why are you soo GOOD AT CHEM!!?!?!?!

Just one thing-- you might want to like explicitly say "thus the use of radioisotopes has improved the health of society as a whole" or something along the lines, just something I've picked up from marking guidelines. I know you imply it and you do have a sentence somewhere but the health of society point I think could be outlined clearly just in case you get a stingy marker. But 5/5 for sure!

NEXT QUESTION PLS

Hahahaha i need to band 6 chem, so answers must be detailed.

ooo okay cool i shall outline it clearer. Thanks

New question: -

Describe the principle of atomic absorption spectroscopy and its application in environmental monitoring. Include a diagram in your answer. 5 marks

 

[mreditor16]

Every cohort in your school is strong. -.-

LOL not every cohort. Personal opinion but I think our 2u maths and English cohorts aren't too great... :/

thanks HPF, I was hoping that my internal rank for english would boost my atar without any work on my part :/

nah but HPF has got a point

this year, our eco, chem and the upper half of 3u cohorts are fairly strong. not sure about bio, but I hear its performing well.

our English cohort is decently good, definitely not bad, but still not you know the best

not sure about the histories and other humanities

4u is quite good, but not wow wow wow calibre. but pretty good.

and phys is quite bad cohort :/

other subjects I forgot?

 

[enigma_1]

What are you ranked?

As long as everyone above you will do well, you shouldn't be affected that much.

I am ranked 12th on a course mark of 88 (yes i know we do not get marks, but it's not hard to calculate them) and 1st is on 92. Literally 4 marks, makes 12 rank difference.

wait what if you go to a crappy school and the people above you are good but then people at the bottom are getting like 5 - 10%??