General Thoughts: Chemistry (1 Viewer)

[emilios]

just curious, what reactions would you guys use when talking about ethanol's role as a solvent? just draw the structural formula?

 

[photastic]

Anyone know scaling of raw marks?

A raw mark of 75-79 (Band 6) gets scaled down by UAC to 84.

just curious, what reactions would you guys use when talking about ethanol's role as a solvent? just draw the structural formula?

Pretty much and labelling the hydrophilic and hydrophobic ends.

 

[mysterymarkplz]

there are no reactions to show its a solvent. you draw its structural formula, account for alkyl group forming dispersion forces with oil, hydroxyl group forming dipole-dipole bonds with hydrogen in water. thus it can dissolve stuff like hexane and water.

 

[emilios]

there are no reactions to show its a solvent. you draw its structural formula, account for alkyl group forming dispersion forces with oil, hydroxyl group forming dipole-dipole bonds with hydrogen in water. thus it can dissolve stuff like hexane and water.

this was the main reason i didn't go for it's role as a solvent :/ i got a bit paranoid in the test coz it said "with reference to underlying chemical reactions/equations" or something to that extent and figured they were hinting at the ethanol --> ethene thing.

not saying what i'm saying is right, just my thought process during the exam.

 

[mysterymarkplz]

Thats fair enough. I chose it cause I knew that was its main use. If you google uses of ethanol, the first thing that comes up is its extensive use as a solvent for chemicals. I feel like the question was more geared towards the society part, the equations and chemical principles just helped raise the standard of your response maybe.

 

[iStudent]

Lol do you think they'd take marks off for not writing dispersion forces? :/ Totally forgot about that haha

 

[mysterymarkplz]

perhaps, you might be able to get away with it if you say like dissolves like and they are both nonpolar.

 

[iStudent]

perhaps, you might be able to get away with it if you say like dissolves like and they are both nonpolar.

Yes I did say that. That was how I learnt it first and it stuck with me :/ (damn teachers lol)

 

[IR]

+1 +1 +1!!

I don't mean this offensively or personally to you IR but I'm just saying in general, we really don't know what the guidelines are. None of us do, and so none of us should pretend we do. We can speculate, but we can't be definite and hence we should refrain from using high modal language.

Tbh I got pretty worried these last few hours because I was just thinking "omg what if they don't take ethanol--->ethylene as valid!?1?!?! 7 marks down the drain mystery mark here I come!!!!!" and seriously no one needs that stress right now (particularly because chem has been on my mind all evening and its really hard to revise for 3u).

In my opinion, it was a valid use as long as you specifically linked it to how ethylene has a benefit on society i.e. simply saying 'ethanol can be used to produce ethylene hence it has a good impact on society' wouldn't be enough, you would need to explain how it is so e.g. polymerisation of ethylene and the products it results in, like I talked about how LDPE is flexible and has applications in plastic bags, enhancing societal convenience etc. The question was an "assess" question so I think personal judgement is allowed. Then again this is my own personal speculation inb4 I get 0, we'll never know.

I do know for a fact that for most 7 mark questions, they expect you to draw from different areas of the syllabus and synthesise them together, which is probably why there's a mark for logical cohesion etc alone. They don't usually have a "students MUST have said this and this" in most extended response guidelines per se, they'll be expecting a range of answers imo.

So basically dw guys. Its over now. Personally I think its valid if you said it was, or wasn't, but we'll have to wait and find out.



OMG THIS WAS ME LOL. I didn't even think of solvent, I just saw chemical equations and I was like "hmm fuel has only one combustion equation. The question has a plural---> must be ethylene dehydration" and then I literally just started filling out the booklets. Then again I had like 10 minutes to do the whole question lol, how I managed to write 2 booklets I have no idea.

Suit yourself.

 

[RealiseNothing]

tbh I have to agree with IR

 

[SuchSmallHands]

The debate about the ethanol question is just getting stupid. If you gave any use of ethanol, explained it's impact on society and the chemistry behind it with relevant equations you have answered the question. If you answer the question you get the marks. The end.

 

[RealiseNothing]

The debate about the ethanol question is just getting stupid. If you gave any use of ethanol, explained it's impact on society and the chemistry behind it with relevant equations you have answered the question. If you answer the question you get the marks. The end.

I guarantee you that's not how it works.

 

[anomalousdecay]

This reminds me of the photocell question in HSC Physics last year.

A solar cell is technically a photocell so it was accepted, despite the fact that the question itself looked as if it wanted an answer in terms of a cell with metal plates.

So its up to the markers and the marking scheme in the end I guess. No point worrying about it now as its done and dusted and whether you get the marks or not is not in your hands any more. Its up to the markers.

 

[Thank_You]

Yeah iStudent is right, how they mark it also depends on how well the quality of answers are, they need to maintain a certain % of high level answers to %of middle range and so on. So if people start talking about fuel and solvents and give brilliant and thorough responses to them, markers begin to lower the standard for people who didn't fuel and solvents. We can all agree that fuel and solvents were their primary focus, but just hope that they also accept esters, polyethene or some other use.

AW man I talked about it as a fuel, but isn't a link to polyethylene any good? It seems pretty good

 

[enigma_1]

Oh wow this debate is still going? I'm not gonna say if either side is right, because I don't know and plus chemistry marking is terribad so no point discussing how they're gonna mark it. Inb4 all our answers are wrong lol

Don't worry about it guys, I bet most of the state was in the same position and the markers will soon realise that it was a dodgy and broad question

 

[OldChemist]

Not only that, considering this test was easier than last year they are going to specifically make it so that you can only use direct uses of ethanol. The only two in syllabus are solvent and fuel.

Well this "debate" has been hilarious. Amazing how certain you are about this... make sure you check out the marking guidelines when they're released.