Tables for Science (1 Viewer)

[CM_Tutor]

Colourimetry is generally working at a singe wavelength, which is used to construct a calibration curve then measure unknowns. similar to AAS.

UV/Vis spectroscopy generally involves scanning the spectrum to produce a graph of absorbance as a function of wavelength.

UV/Vis can be carried out on a single wavelength, though, too.

Note, though, that far more important to this question is that analytical techniques like MS do not involve monitoring changes in intensity of light at all.

 

[dasfas]

No this is a myth. Why would a student be penalised for a minor formatting issue? The purpose of the exam is to check you understand the content not to be marking people for such a small thing

These are band 5-6 responses for questions to the HSC 2019 Chemistry Exam as determined by the people marking the exam:

https://educationstandards.nsw.edu.au/wps/wcm/connect/4e4f53a4-fe6b-4c67-be06-1efe61dc9153/2019+HSC+-+Chemistry+++-+2019+HSC+-+Chemistry+Section+2+Q21-34+Band+5-6+Sample+1.pdf?MOD=AJPERES&CACHEID=ROOTWORKSPACE-4e4f53a4-fe6b-4c67-be06-1efe61dc9153-nxnY81X

Go to page 25 you can clearly see a table without closed boxes for a RICE table.

Wow hahaha, I recognise some of that handwriting

 

[idkkdi]

Wow hahaha, I recognise some of that handwriting

, handwriting reveal?
the amount of spelling errors in those samples haha.

 

[idkkdi]

the amount of spelling errors in those samples haha.

some of these answers are quite interesting.

"lower tripod" for enthalpy of combustion. interestingly enough, i don't think i've seen different tripod heights in the school lab lol.

 

[jazz519]

some of these answers are quite interesting.

"lower tripod" for enthalpy of combustion. interestingly enough, i don't think i've seen different tripod heights in the school lab lol.

They probably mean the clamp and retort stand. I guess if the question is not worth heaps and they can understand what the student is trying to suggest they might be a bit lenient

 

[someth1ng]

@someth1ng, a 6 mark question that I have found from a 2020 Trial that you might like...

What school was this? But yeah, I don't even know where to start.

There's too many things wrong...the detector changes, the light source changes, NMR is a completely different system (requires magnetic fields, radio waves are detected), there's also fluorescence spectroscopy which doesn't measure the light absorbed (detection is at 90 degrees from the light source)...and there seems to be a million ways IR is measured (e.g. neat, film, KBr...). Oh yeah, there are also Shigemi tubes in NMR for low concentration work.

what is actually different between uv-vis and colourimetry other than the light source?

chem in focus seems to want to say uv-vis is the one with chromophores absorbing light.
aren't chromophores also the one absorbing the light in colourimetry.

It seems like UV-Vis is visible plus UV, colorimetry is just visible. The funny thing is, today is the first day I've heard of colorimetry...I've only used/seen UV-Vis.

 

[CM_Tutor]

They probably mean the clamp and retort stand. I guess if the question is not worth heaps and they can understand what the student is trying to suggest they might be a bit lenient

Looking at the diagram in the question, the tripod and gauze on which the beaker is sitting is a long way above the flame of the burner. Reducing this gap with a shorter tripod would reduce heat loss, so the idea is sound, even if the implementation might be easier by placing the spirit burner on a non-flammable block to raise the flame towards the beaker.

 

[CM_Tutor]

What school was this? But yeah, I don't even know where to start.

There's too many things wrong...the detector changes, the light source changes, NMR is a completely different system (requires magnetic fields, radio waves are detected), there's also fluorescence spectroscopy which doesn't measure the light absorbed (detection is at 90 degrees from the light source)...and there seems to be a million ways IR is measured (e.g. neat, film, KBr...). Oh yeah, there are also Shigemi tubes in NMR for low concentration work.

My point was, the question presents the idea that all analytical techniques are basically shine light through and measure absorbance, and asks students to evaluate it. The could certainly go for the differences in NMR, or fluorescence not being absorbance (not that fluorescence spectroscopy is studied), but they can explore that IR can be transmittance, or more importantly, that MS as an analytical technique is not based on light at all. The question could be improved, sure, but it is actually pointing to the fact that not all analysis is spectroscopic, which I think is a good thing.

It seems like UV-Vis is visible plus UV, colorimetry is just visible. The funny thing is, today is the first day I've heard of colorimetry...I've only used/seen UV-Vis.

Colorimetry is often done with a hand-held unit that operates at only a single wavelength at a time, with limited choices of wavelength.

 

[someth1ng]

My point was, the question presents the idea that all analytical techniques are basically shine light through and measure absorbance, and asks students to evaluate it. The could certainly go for the differences in NMR, or fluorescence not being absorbance (not that fluorescence spectroscopy is studied), but they can explore that IR can be transmittance, or more importantly, that MS as an analytical technique is not based on light at all. The question could be improved, sure, but it is actually pointing to the fact that not all analysis is spectroscopic, which I think is a good thing.


Colorimetry is often done with a hand-held unit that operates at only a single wavelength at a time, with limited choices of wavelength.

I guess I've been out of HS for too long that I'm not entirely where the line between HS and university is anymore lol. As for the question, it's one of those things where being too broad/vague can make it very difficult.

Also calorimetry, I was just reading online over it and the impression I got was that it was basically the same as UV-Vis lol. I guess I haven't seen it because you can do everything using a single wavelength on a normal UV-Vis.

 

[idkkdi]

I guess I've been out of HS for too long that I'm not entirely where the line between HS and university is anymore lol. As for the question, it's one of those things where being too broad/vague can make it very difficult.

Also calorimetry, I was just reading online over it and the impression I got was that it was basically the same as UV-Vis lol. I guess I haven't seen it because you can do everything using a single wavelength on a normal UV-Vis.

colourimeter literally uv-vis in a box. schools can't afford uv-vis lol.