Chemistry Marathon (HSC) (1 Viewer)

[someth1ng]

Really? I like industrial chem (except for saponification). Anyway, back to the idea of this thread:

A student said that the use of ethanol as a fuel is entirely carbon neutral. Evaluate this statement with appropriate equations

Ethanol is sometimes considered as a carbon neutral fuel however its production often releases some amount of CO2.

Ethanol is considered a carbon neutral fuel because CO2 used to produce the reactants for the production of ethanol is equal to the CO2 produced during the fermentation of glucose to produce ethanol and the combustion of ethanol and hence, net carbon release to the atmosphere is zero.

Glucose, the raw material for ethanol production is derived from plants is produced from CO2 and water by photosynthesis in plants using chlorophyll as a catalyst.
6CO2+6H2O-(photosynthesis)->C6H12O6+6O2

The glucose is fermented using yeast to produce CO2 and ethanol.
C6H12O6-(yeast)->2C2H5OH+2CO2

The ethanol can then be combusted as a fuel:
C2H5OH+3O2-->2CO2+3H2O

Evidently, overall, the whole process can be shown as a cycle: 6CO2+6H2O-(photosynthesis)->C6H12O6+6O2-(yeast)->2C2H5OH+2CO2+6O2-->6CO2+6H2O
Therefore, ethanol is seen as a carbon neutral fuel as all carbon released is absorbed and vice versa. This means that the student is correct in saying that ethanol is a carbon neutral fuel.

Although the student is correct in saying that it is carbon neutral but it is not entirely carbon neutral because the student did not consider other any possible energy considerations that is required in the process that may emit CO2.
1. The process requires the harvesting of glucose, often from sugar cane, which will most likely require energy - often supplied from petroleum, a non-carbon neutral resource, causing more CO2 to be released into the atmosphere.
2. Fermentation requires an input of energy to maintain a warm temperature in the fermentation vats. The source of energy is often sources from fossil fuels, a non-carbon neutral resource, meaning that there is a net release of CO2 into the atmosphere.
3. Transportation of ethanol for its use requires energy to be input, often from petroleum (octane), a non-renewable and non-carbon neutral resource and hence, releasing more CO2 into the atmosphere.
C8H18+(25/2)O2-->8CO2+9H2O
4. Fractional distillation is often required to produce suitably pure amounts of ethanol to be useful. This means that it is not carbon neutral because fractional distillation required high amounts of thermal energy which is often from the burning of other, often non-renewable, fuel sources such as petroleum.

Although the student was partially correct in stating that ethanol is a carbon neutral fuel, it is not entirely a carbon neutral fuel as the process to produce ethanol requires extra energy input, usually from fossil fuels or other non-renewable resources and hence, making ethanol only partially carbon neutral.

Note: I am aware that my equations do not have states, I didn't include them because it would make the equations messy and harder to read.

 

[madharris]

Ethanol is sometimes considered as a carbon neutral fuel however its production often releases some amount of CO2.

.....

Although the student was partially correct in stating that ethanol is a carbon neutral fuel, it is not entirely a carbon neutral fuel as the process to produce ethanol requires extra energy input, usually from fossil fuels or other non-renewable resources and hence, making ethanol only partially carbon neutral.

wow... nice work... i forgot all about the student. That's what i get when i don't high light a question

 

[Sanjeet]

1. Write out the equilibrium expression
2. We want to replace everything that is not [H+] with either [H+] or a constant
3. We know from standard ionisation that [H+] = [CH3COO-]
4. as 0.5 mol/L of Acetic acid is originally placed in the beaker, and these molecules either stay in their molecular form or ionise, we can say that [H+] + [CH3COOH] = 0.5
5. Replace all things other than [H+]
6. Solve quadratic taking the positive solution
7. Use pH = -log[H+]
8. Presto!

Is this the only solution? I don't think they can assume you know the quadratic formula lol

 

[barbernator]

Is this the only solution? I don't think they can assume you know the quadratic formula lol

yeh its the only way. its just a harder question that can't be asked in the HSC anyway.

 

[someth1ng]

wow... nice work... i forgot all about the student. That's what i get when i don't high light a question

Yeah, just make sure you answer all of question.

Also, I'd recommend going into more detail with your disadvantages. You might want to include HOW your example is true.
"In the fermentation process we also only gain 15% ethanol, meaning more energy is used in the process, creating more CO2"
HOW is more energy released? You should talk about needing to make it pure and that's HOW energy is needed.

 

[madharris]

Yeah, just make sure you answer all of question.

Also, I'd recommend going into more detail with your disadvantages. You might want to include HOW your example is true.
"In the fermentation process we also only gain 15% ethanol, meaning more energy is used in the process, creating more CO2"
HOW is more energy released? You should talk about needing to make it pure and that's HOW energy is needed.

ok thanks for that

 

[crazy_paki123]

howd u guyys remember everything for industrial. so annoying especially production of NaOH -.-

 

[B3A13]

howd u guyys remember everything for industrial. so annoying especially production of NaOH -.-

I know. it really sucks. our teacher didnt even give us a choice.

 

[LoveHateSchool]

Another industrial hater...would have loved to do forensics, or even the art one. Or even biochem of movement.

Though glad we didn't do Shipwrecks.

 

[crazy_paki123]

Another industrial hater...would have loved to do forensics, or even the art one. Or even biochem of movement.

Though glad we didn't do Shipwrecks.

i actually like everything in industrial chem, just hate the productions of NaOH

 

[ellie95]

i actually like everything in industrial chem, just hate the productions of NaOH

Personally that is so much easier than the Solvay Process for me

 

[kwu1]

Can someone please explain how a Geiger muller tube works? Thanks

 

[timeslowsdown]

Can someone please explain how a Geiger muller tube works? Thanks

Geiger muller tubes are based on the ionising properties of radiation, hence most effective for measuring alpha + beta radiation. So essentially the radiation enters the tube, and collides with gas molecules within (predominantly argon is used), and ionises the gas i.e removes an electron. The voltage applied to the tube accelerates this electron towards the central electron, and in doing so, gains energy, ionises more argon molecules, causing more electrons to reach the electrode. The electrons reaching the electrode forms an electric signal, generating a series of clicks or a reading for an electronic digital counter. So all in all, gieger muller tubes measure the amount of radiation present by using their ionising ability i.e the more radiation present, the more electrons will be produced.

 

[timeslowsdown]

Really? I like industrial chem (except for saponification). Anyway, back to the idea of this thread:

A student said that the use of ethanol as a fuel is entirely carbon neutral. Evaluate this statement with appropriate equations

The student may perceive ethanol to be entirely carbon neutral due to the fact that ethanol is a renewable source, that can be produced from the fermentation of cellulose (which can be derived from biomass i.e plant matter, via photosynthesis):

6CO2 + 6H2O + UV light > C6H12O6 + 6O2

Cellulose derived from crops can be converted into glucose via heating with conc. sulfuric acid or digestion by cellulase enzymes found in the guts of herbivores. Glucose can thus be fermented to produce ethanol:

C6H12O6 > 2C2H5OH + 2CO2

Ethanol would thus be combusted by vehicles:

C2H5OH + 7/2O2 > 2CO2 + 3H2O

So theoretically, the student is correct in saying that ethanol is a carbon neutral fuel, in that through its production, CO2 is absorbed by crops, and thus released via combustion.

HOWEVER, this claim does not take into account the CO2 emissions produced throughout ethanol's production. That is, the fertilisers required for the growth of crops (which provide the source of glucose) require the burning of fossil fuels in their production. Furthermore, fermentation in isolation only produced 15% ethanol, as the ethanol destroys the yeast that catalyses this reaction, and hence fails to produce more ethanol beyond this point. So ethanol needs to be distilled to attain greater concentrations, which requires a large amount of electricity which is primarily sources from the burning of fossil fuels.

All in all, the student's claim is incorrect, as the energy required for distillation and the production of fertilisers needed for the cultivation of crops is predominantly sourced from the burning of fossil fuels. Yet the claim could be correct if renewable sources of energy are used, which do not produce CO2 emissions.

 

[kwu1]

Geiger muller tubes are based on the ionising properties of radiation, hence most effective for measuring alpha + beta radiation. So essentially the radiation enters the tube, and collides with gas molecules within (predominantly argon is used), and ionises the gas i.e removes an electron. The voltage applied to the tube accelerates this electron towards the central electron, and in doing so, gains energy, ionises more argon molecules, causing more electrons to reach the electrode. The electrons reaching the electrode forms an electric signal, generating a series of clicks or a reading for an electronic digital counter. So all in all, gieger muller tubes measure the amount of radiation present by using their ionising ability i.e the more radiation present, the more electrons will be produced.

Thanks. By the way, typo it's central electrode. From what I have read from other sources, the positive ions (argon) are attracted to the anode. Meanwhile, the electrons are attracted to the cathode, thereby forming a circuit and allowing the micro current to be interpreted and therefore, the level of radiation.

 

[timeslowsdown]

Thanks. By the way, typo it's central electrode. From what I have read from other sources, the positive ions (argon) are attracted to the anode. Meanwhile, the electrons are attracted to the cathode, thereby forming a circuit and allowing the micro current to be interpreted and therefore, the level of radiation.

Lol sorry about that. Thanks for the additional info!

 

[kwu1]

Lol sorry about that. Thanks for the additional info!

 

[J-Wang]

Analyse the relationship between the position of elements in the Periodic Table, and the acid-base behaviour of their oxides (4mrk)

 

[deswa1]

Analyse the relationship between the position of elements in the Periodic Table, and the acid-base behaviour of their oxides (4mrk)

I'll just dot point this but essentially:

- The basicity of an elements oxide is related to its metallic character
- As you move from right to left in a period, metals become less metallic and hence more acidic. They move from basic oxides (such as sodium oxide) to amphoteric oxides which can act as both acids and bases (such as aluminium oxide) to acidic oxides (such as carbon dioxide)
- As you move down a group, the element becomes more metallic in nature and hence more basic
- Nobel gases don't form oxides.

Question: Describe an experiment where you measured the sulfate concentration of fertiliser. In your response, refer to any assumptions you made that might have compromised the validity of the prac and things you could do to fix these

 

[Sanjeet]

Hey guys I just had a quick question (sorry deswa lol)

What makes ozone more reactive that oxygen? Is it because the co-ordinate covalent bond is weak? If so, what makes it weaker than an ordinary covalent bond?
And what makes ozone slightly polar? It's a bent molecule but its net dipole is 0.