ATAR Notes: Forum
Archived Discussion => 2010 => Mid-year exams => Exam Discussion => Victoria => Chemistry => Topic started by: matt123 on June 09, 2010, 03:31:57 pm
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the question about the boiling points
its like .. out of the volatile gases .. pick one which isnt a part of the sample
i said methanol? .. was that correct?
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Could have used methanol or ethanol couldnt you ?
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yeah im pretty sure
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Methanol or ethanol would have sufficed. This is because the first fraction collected is at 97.2 degrees. If methanol or ethanol were present in the sample, then the first fraction would have been collected at a lower temperature
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i said methanol woo!
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huh???i forgot the question...
why?
could someone explain?
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isnt it butanol and pentanol
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Nope, question asked which couldnt be in the mixture.
If methanol or ethanol were in the mixture then they would come out first but they didnt.
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But it's lab fracional distillation...
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Nope, question asked which couldnt be in the mixture.
If methanol or ethanol were in the mixture then they would come out first but they didnt.
how[ do u know they didnt?
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isnt it butanol and pentanol
I did this too.... I'm shattered and it's all cause I misread the question!!!!!!!
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mao is saying it would me butan ol and pentan ol
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Nope, question asked which couldnt be in the mixture.
If methanol or ethanol were in the mixture then they would come out first but they didnt.
how[ do u know they didnt?
Because the Question said that the first fraction was at 97.2, which corresponds to propanol..
so anything less can't be the mixture. Plus only 2 Alcohols were tested..
Souljette
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As much of a genius Mao is , i think hes wrong :)
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Also got it wrong, why do I always not read the damn question properly. >:(
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used the same logic as you Souljette
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what did use get for Question 4
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Can't use bunsen burner because temp. can't be controlled right?
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Can't use bunsen burner because temp. can't be controlled right?
I said same. cant control temperature therefore hard to separate easily.
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what did use get for Question 4
4a) A,D
b) hydrogen bonding
c) C,F
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Can't use bunsen burner because temp. can't be controlled right?
Who knows. Honestly think VCAA will accept different answers. it can't just only be one.
Souljette
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It's a little confusing cause the last sentence states "The first fraction is collected at 97.2 C" and the question asks to identify what will not be present in this mixture. There are really two mixtures, firstly the fraction which has 3 different vapours and the liquid. Really comes down to interpretation, but I think VCAA was referring to the liquid mix.
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Can't use bunsen burner because temp. can't be controlled right?
I wrote sumthing along the lines of Bunsen Burner causes rapid heating...
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I'm interested to see what mao thinks is the answer to this in his completed suggested answers!!
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I wrote sumthing along the lines of Bunsen Burner causes rapid heating...
Yeah I had something similar, the bunsen would heat one area much more than the rest etc.
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This is what Mao said "Alkanols are volatile and combustible. Alkanol vapours are in fact explosive. Using a naked flame (bunsen burner) is a serious hazard in dealing with these chemicals."
He should've also added that alkanols are flammable. Basically if you wrote the word flammable then that answers the question. Naked flame does not mix with flammable material
And with the first part of the question, I misread it the first time and thought one of the heavier alkanols. You pretty much had to look at the keywords and notice it said "first fraction"
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This is what Mao said "Alkanols are volatile and combustible. Alkanol vapours are in fact explosive. Using a naked flame (bunsen burner) is a serious hazard in dealing with these chemicals."
He should've also added that alkanols are flammable. Basically if you wrote the word flammable then that answers the question. Naked flame does not mix with flammable material
And with the first part of the question, I misread it the first time and thought one of the heavier alkanols. You pretty much had to look at the keywords and notice it said "first fraction"
I think when Mao says "combustible" he covers himself in terms of "flammable"...
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yeah he is... but stuffed up the last question where ti was butane -117 degrees and propanol 97 degrees i thot 117 wasnt negative so i did it the other way around fml ==' 42/75 dreadful and i studied my arse off
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yeah he is... but stuffed up the last question where ti was butane -117 degrees and propanol 97 degrees i thot 117 wasnt negative so i did it the other way around
I did the saaame thing. lol