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