ATARNotes Suggested Solutions for VCAA 2012 Chemistry Unit 3 Exam

[AllAboutTheLGs]

^ yeah dude lets rape the unit 4 exams

[arikupe2]

with working out the average iron content in the tablets, shouldn't the answer be 30mg as opposed to 36?

Because they gave us a standard solution of concentration 0.00g/L of tablet that still absorbed some of the radiation (0.006 abs), implying some Fe was present as impurities in the water used to dissolve the tablets (it also didn't say 'deionized water')... Then if we're working out the amount of Fe in the tablets, wouldn't you need to discount the amount of impurity also absorbing some radiation (equivalent to 6mg of Fe in the water)?

Or is that looking too much into it?

[nina_rox]

For stearic acid could the state be a gas? :/

[Surgeon]

How many marks would I lose if I wrote tristearic acid instead of stearic acid and my balancing was out by a factor of 3?

[shmootz]

with working out the average iron content in the tablets, shouldn't the answer be 30mg as opposed to 36?

Because they gave us a standard solution of concentration 0.00g/L of tablet that still absorbed some of the radiation (0.006 abs), implying some Fe was present as impurities in the water used to dissolve the tablets (it also didn't say 'deionized water')... Then if we're working out the amount of Fe in the tablets, wouldn't you need to discount the amount of impurity also absorbing some radiation (equivalent to 6mg of Fe in the water)?

Or is that looking too much into it?

It could also be an absorbance of the cell... that's the point of using a 'blank' initially. I didn't take off 6mg, but others did and I think they are right..

- Stone

[illuminati]

with working out the average iron content in the tablets, shouldn't the answer be 30mg as opposed to 36?

Because they gave us a standard solution of concentration 0.00g/L of tablet that still absorbed some of the radiation (0.006 abs), implying some Fe was present as impurities in the water used to dissolve the tablets (it also didn't say 'deionized water')... Then if we're working out the amount of Fe in the tablets, wouldn't you need to discount the amount of impurity also absorbing some radiation (equivalent to 6mg of Fe in the water)?

Or is that looking too much into it?

It could also be an absorbance of the cell... that's the point of using a 'blank' initially. I didn't take off 6mg, but others did and I think they are right..

- Stone

err, nah they'd be wrong
It's because it says the concentration is 0 when you have absorbance at 0.06. Impurities were therefore never counted as part of the concentration.

[Louise clover]

hi there, jst a few confusing points, for the fatty acid identification question, i put down stearic instead of stearic acid, is that goin to get me zero marks? for the technique to identify the pure propyl ester i put down hplc, instead of glc, and one  last mistake i think i made was that i chose to describe IR spectroscope as the technique we learnt this unit and i only mentioned bond energy instead of bond length and strength, is that wrong?

sorry, that i have many questions, im a bit nervous.

Thank you!

[jenwing]

Posted by: Louise clover
« on: 9 hours ago » Insert Quote
hi there, jst a few confusing points, for the fatty acid identification question, i put down stearic instead of stearic acid, is that goin to get me zero marks? for the technique to identify the pure propyl ester i put down hplc, instead of glc, and one  last mistake i think i made was that i chose to describe IR spectroscope as the technique we learnt this unit and i only mentioned bond energy instead of bond length and strength, is that wrong?

sorry, that i have many questions, im a bit nervous.

Thank you!

-I did the exact same thing...

[Louise clover]

how many marks would they take off if i have the correct balanced equation but maybe one or more wrong states?

[thushan]

how many marks would they take off if i have the correct balanced equation but maybe one or more wrong states?

you'd get 1/2

[thushan]

hi there, jst a few confusing points, for the fatty acid identification question, i put down stearic instead of stearic acid, is that goin to get me zero marks? for the technique to identify the pure propyl ester i put down hplc, instead of glc, and one  last mistake i think i made was that i chose to describe IR spectroscope as the technique we learnt this unit and i only mentioned bond energy instead of bond length and strength, is that wrong?

sorry, that i have many questions, im a bit nervous.

Thank you!

stearic? hmm that'd be touch and go. i'd pay it, but I'm not sure of the chief examiner though. chances are he'll pay it, apparently he's quite fair

bond energy is fine. bond length, strength, energy, they're talking about the same thing. as for hplc, you may get away with it, i'm not entirely sure.

[Louise clover]

how do we get consequencial marks in a chemistry exam, because i put down propanol instead of propan-1-ol, and i did the same thing in the flowchart that describes how we could extract pure propyl propanoate, but when i write down the semistructural formulae, i put down propan-1-ol. would i loose alot of marks for this?   

[Louise clover]

hi there, jst a few confusing points, for the fatty acid identification question, i put down stearic instead of stearic acid, is that goin to get me zero marks? for the technique to identify the pure propyl ester i put down hplc, instead of glc, and one  last mistake i think i made was that i chose to describe IR spectroscope as the technique we learnt this unit and i only mentioned bond energy instead of bond length and strength, is that wrong?

sorry, that i have many questions, im a bit nervous.

Thank you!

stearic? hmm that'd be touch and go. i'd pay it, but I'm not sure of the chief examiner though. chances are he'll pay it, apparently he's quite fair

bond energy is fine. bond length, strength, energy, they're talking about the same thing. as for hplc, you may get away with it, i'm not entirely sure.

thank you so much  thushan!

[thushan]

hi there, jst a few confusing points, for the fatty acid identification question, i put down stearic instead of stearic acid, is that goin to get me zero marks? for the technique to identify the pure propyl ester i put down hplc, instead of glc, and one  last mistake i think i made was that i chose to describe IR spectroscope as the technique we learnt this unit and i only mentioned bond energy instead of bond length and strength, is that wrong?

sorry, that i have many questions, im a bit nervous.

Thank you!

stearic? hmm that'd be touch and go. i'd pay it, but I'm not sure of the chief examiner though. chances are he'll pay it, apparently he's quite fair

bond energy is fine. bond length, strength, energy, they're talking about the same thing. as for hplc, you may get away with it, i'm not entirely sure.

thank you so much  thushan!

no worries!

[BambooPanda]

Hi guys, for the question that asked how the sample can be tested to be pure I wrote GC but said something along the lines of:
If only one peak is present in addition to the carrier gas peak (assuming carrier gas produces a peak) then the sample is likely to be pure.

Last night I just remembered that the carrier gas is inert and won't produce a peak... So I'm wondering if I would get atleast 1 mark out of the 2 marks allocated for the question?