Predictions for Chemistry 2014 HSC? (12 Viewers)

[SuchSmallHands]

Here's a question that I found to be absolutely impossible to get full marks on from my trial, if anyone wants to have a go.

Which allotrope [oxygen or ozone] would you expect to have a higher boiling point? Justify your answer. (2 marks)

PS. you must have 2 reasons

I would expect ozone to have a higher boiling point. Reasons:
- It is a bent molecule, thus it has a slight dipole moment, while the diatomic oxygen molecule is linear.
- It has a higher molecular weight that oxygen.

 

[enigma_1]

Thank god, I was worried for your health there. 3U French, Legal, Modern, 4U English and then, out of no where, I chose Chemistry. Everyone is still confused as to what the hell I'm doing in that class. I've read a lot of books in the days before the HSC destroyed any love of literature I started with, so it's not that hard for me to source sophisticated related texts (I tend to use Anna Karenina for like everything, since it's the best book ever written and all, so I have some background on that if I want to use it for belonging too). Besides I did poetry for EE2, so I researched a million really short related texts there haha. I don't really know what my on the spot essays will score in the HSC, my teacher is a super relaxed marker and only acknowledged that one of my crappy trial essays was crappy (he gave me 15 for Belonging and 20, 19 and 16 for modules). I think a HSC marker would have smashed them though. So yeah, moral of the story, I should go find related texts as soon as I can.

Whoaa that's such a heavy workload!
I'm in awe at the way you are managing all this
That's still very good, my essays for my modules were like 13, 15 and 17 so yeah extremely bad. The 13 one I wrote on the sport so there you go ahahah my English skills are terribad.

Yeah defs. And if there's nothing left you can choose a movie/book that you enjoy eg I have TKAM as a backup for belonging because I absolutely love it, know the story by heart and read it heaps.

All the best!

 

[faisalabdul16]

Preparing my anus for an onslaught of titration questions. And a long mark question on some random scientist I will no doubt forget to study. Praying hard for long answers on ozone and acid rain, but I doubt we will get let of that easy..

No ozone, it was big marks in last years paper. Hopefully acid rain, but then the whole state will probably ace that.

Admittedly, that's probably true.

Yes. Because then you have to analyse it and incorporate into your essay.

I remember this was in hsc, I'll pretend that I remember the extract. It was something about a car manufacturer iirc.

Ethanol is a renewable resource as it is naturally obtained from cellulose which is a major component of biomass, equating to 50% of it. Firstly the cellulose is obtained from crops such as sugar cane and corn. The cellulose then undergoes enzymatic/acid digestion with concentrated 5 mol/L sulphuric acid to be broken down into Glucose. The glucose is then fermented (reactions conditions: 37 degrees Celsius, anaerobic environment to prevent the ethanol from oxidising into ethanoic acid [vinegar], presence of sulphate to prevent growth of bacteria,15% ethanol concentration, yeast enzymes: zymase, nitrates and phosphates: yeast nutrients and glucose).

Fermentation: C6H1206(aq) ------yeast enzymes, 37 degC ----> 2CO2(g) + 2C2H5OH(aq)

This produces 15% ethanol concentration which can be distilled to obtained higher concentrations such as ~ 95%.

Ethanol has several advantages for it's use:
1) Ethanol is a carbon neutral fuel because the CO2(g) released upon combustion of ethanol:

C2H5OH(aq) + 3O2(G) -----> 2CO2(g) + 3H2O(L)

is equivalent to the amount of carbon dioxide used in its photosynthesis.

6CO2(g) + 6H2O(l) ----sunlight/chlorophyll -- C6H12O6(aq) + 6O2(g)

2) Ethanol is a renewable resource as it is obtained from biomass, so it is a better alternative than octane which is obtained from non-renwable fossil fuels.

3) Ethanol is more likely to undergo complete combustion which does not produce any pollutants such as carbon (soot) or CO (which binds to haemoglobin 10 times faster than oxygen, preventing oxygen intake): eqn is above

[insert equation for combustion of octane here, releasing pollutants]

Disadvantages of using ethanol:
1) Ethanol at present is not economically viable as a complete replacement because

2) Ethanol to be used in concentrations greater than 10% in engines require engine modifications to prevent knocking.

3) For the plants and crops to be planted in third world countries, it would mean that resources are allocated to planting crops for ethanol production rather than for food in third world countries which could result in famine and is hence unfavourable.

4) Ethanol is not completely a carbon neutral fuel because during the distillation of ethanol, fossil fuels are utilised and this process also releases CO2(g) into the atmosphere, thus it not technically carbon neutral

EVALUATION: Ethanol is a renewable resource, however the extract (since it is written by a leading car manufacturer) fails to make reference to the CO2 released during other processes and thus the ethanol is NOT carbon neutral. The leading car manufacturer’s article is not accurate because it is not a reliable source and thus the statements made are not scientifically correct.

wow.... fullmarks! Prety solid

Here's a question that I found to be absolutely impossible to get full marks on from my trial, if anyone wants to have a go.

Which allotrope [oxygen or ozone] would you expect to have a higher boiling point? Justify your answer. (2 marks)
PS. you must have 2 reasons

Ozone would have a higher boiling point due to more dispersion forces being present than oxygen. More dispersion forces requires a greater amount of energy to break the bonds and hence ozone will have a higher boiling point than oxygen. WTF IS A SECOND REASON =( I made three google searches and they only mention what i said already.

 

[Cleverusername5321]

I would expect ozone to have a higher boiling point. Reasons:
- It is a bent molecule, thus it has a slight dipole moment, while the diatomic oxygen molecule is linear.
- It has a higher molecular weight that oxygen.

I think that's correct. The only thing is that my teacher used the term "it has more moving electrons" to explain why it has more induced dipole moments, giving it greater polarity and thus a higher boiling point. (I'm really not sure, I don't fully understand it).

Another funsie: a) In North America the acid rain has been recorded at a pH of 3. Sulfur dioxide could cause this pH. What is the concentration of the hydrogen ions in the rain water.
b) Assuming all the sulfur dioxide fully dissociates, what volume of gas is dissolves in 300 mL of rain water at 0 degrees C and 100 kPa.

(1 mark each)

The first one is easy, but you need it for the second one.

 

[SuchSmallHands]

Whoaa that's such a heavy workload!
I'm in awe at the way you are managing all this
That's still very good, my essays for my modules were like 13, 15 and 17 so yeah extremely bad. The 13 one I wrote on the sport so there you go ahahah my English skills are terribad.

Yeah defs. And if there's nothing left you can choose a movie/book that you enjoy eg I have TKAM as a backup for belonging because I absolutely love it, know the story by heart and read it heaps.

All the best!

Better than what I would have got if my trials had been marked harshly!

 

[faisalabdul16]

So it's polarity gives it a higher boiling point as well.

Interesting

 

[seventhroot]

Now she deserves to be in the 2 day ~mech master race ~ brahhh

nah

 

[SuchSmallHands]

I think that's correct. The only thing is that my teacher used the term "it has more moving electrons" to explain why it has more induced dipole moments, giving it greater polarity and thus a higher boiling point. (I'm really not sure, I don't fully understand it).

Another funsie: a) In North America the acid rain has been recorded at a pH of 3. Sulfur dioxide could cause this pH. What is the concentration of the hydrogen ions in the rain water.
b) Assuming all the sulfur dioxide fully dissociates, what volume of gas is dissolves in 300 mL of rain water at 0 degrees C and 100 kPa.

(1 mark each)

The first one is easy, but you need it for the second one.

I'll do this when I have my calculator (anyone else can attempt it in the meantime obviously). That's a cool calc though, different to what we usually get, where did you find it?

 

[Cleverusername5321]

So it's polarity gives it a higher boiling point as well.

Interesting

I'm pretty sure that polarity = stronger intermolecular forces, and for something to boil you need to break intermolecular forces. Someone correct me if I'm wrong.

 

[SuchSmallHands]

So it's polarity gives it a higher boiling point as well.

Interesting

Yep, I think it has like 0.51 or 0.53 D dipole moment (can't remember exactly, I'm not that good haha)

 

[Cleverusername5321]

I'll do this when I have my calculator (anyone else can attempt it in the meantime obviously). That's a cool calc though, different to what we usually get, where did you find it?

Test that was used in my school for the acidic environment.

 

[enigma_1]

Better than what I would have got if my trials had been marked harshly!

ahaha no way, I doubt it! You're a humanities girl!
@cleverusername

Oh wow that justification from your teacher - for hsc I wouldn't think that's necessary.

 

[enigma_1]

nah

k den

jks mech is not even 4 me

 

[seventhroot]

k den

jks mech is not even 4 me

 

[enigma_1]

haha fckk this is hilarious

http://weknowmemes.com/wp-content/uploads/2012/08/slenderman-still-more-facial-expressions.jpg

 

[QZP]

Yep, I think it has like 0.51 or 0.53 D dipole moment (can't remember exactly, I'm not that good haha)

Why do you know so much random information T_T You make me doubt myself. Further example in your response:

"Satellite based instruments can be used to detect ozone concentration in the stratosphere. Following calibration issues with the last Total Ozone Mapping Spectrometer (TOMS) unit in orbit, they were replaced in 2007 by the Ozone Mapping Instrument operated from the NASA Aura. Satellite based instruments map differences in incoming solar energy and backscattered UV light across earth. In doing so, these instruments highlight areas if weakness in the ozone layer by noting the failure of the ozone layer to absorb UV light.
The Donson Ozone Spectrophotometer is a ground based izone concentration detection system that is less precise than satellite based models and thus primarily used for corroborating satellite data. It works by measuring the amount if one wavelength of UVA radiation reaching earth, which does not have the energy to photolysise ozone and thus is not absorbed by the ozone layer, against one wavelength of UVB radiation, which does have the energy to photolysise ozone and thus will reach earth in an amount which is directly proportional to ozone concentration in the stratosphere."

Bold: never heard of such things. Am i going to get b5
My understanding is basically Satellite-based TOMS: Measure ozone concentration at various altitudes and geographical locations (no idea how; where did you learn this?), resulting in an ozone concentration map
Ground-based spectrophotometers: In a vertical column, measures intensity of a wavelength characteristically absorbed by UV-B and UV-C, which is then compared to a different wavelength to measure total-column ozone in Dobsin units DU

Red: Do you mean inversely proportional?

 

[QZP]

Industrial: Describe how the products of electrolysing dilute and concentrated NaCl solution could be identified (4)

I was stuck on this fml (WTF I NEVER LEARNT TO IDENTIFY CL2)

 

[faisalabdul16]

is a) 0.001. Am i missing something? or is it as simple as follows.

 

[Cleverusername5321]

is a) 0.001. Am i missing something? or is it as simple as follows.

That's correct. Like I said, it was an easy question, but it's required for b).
Also, you should probably mention units which is mol/L.

 

[enigma_1]

Why do you know so much random information T_T You make me doubt myself. Further example in your response:

"Satellite based instruments can be used to detect ozone concentration in the stratosphere. Following calibration issues with the last Total Ozone Mapping Spectrometer (TOMS) unit in orbit, they were replaced in 2007 by the Ozone Mapping Instrument operated from the NASA Aura. Satellite based instruments map differences in incoming solar energy and backscattered UV light across earth. In doing so, these instruments highlight areas if weakness in the ozone layer by noting the failure of the ozone layer to absorb UV light.
The Donson Ozone Spectrophotometer is a ground based izone concentration detection system that is less precise than satellite based models and thus primarily used for corroborating satellite data. It works by measuring the amount if one wavelength of UVA radiation reaching earth, which does not have the energy to photolysise ozone and thus is not absorbed by the ozone layer, against one wavelength of UVB radiation, which does have the energy to photolysise ozone and thus will reach earth in an amount which is directly proportional to ozone concentration in the stratosphere."

Bold: never heard of such things. Am i going to get b5
My understanding is basically Satellite-based TOMS: Measure ozone concentration at various altitudes and geographical locations (no idea how; where did you learn this?), resulting in an ozone concentration map
Ground-based spectrophotometers: In a vertical column, measures intensity of a wavelength characteristically absorbed by UV-B and UV-C, which is then compared to a different wavelength to measure total-column ozone in Dobsin units DU

Red: Do you mean inversely proportional?

ahah it's ok dude, that's what this thread is for.
You can figure out which things you didn't know before and incorporate them into your memory.