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March 28, 2024, 07:15:46 pm

Author Topic: VCE Chemistry Question Thread  (Read 2312955 times)  Share 

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Mattjbr2

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Re: VCE Chemistry Question Thread
« Reply #7695 on: December 04, 2018, 11:43:30 am »
+2
Sweetcheeks was using the excitation of electrons as a comparison to explain the nucleus flipping - might be worth a reread :)

I realized and edited my response. Still nowhere closer to the answer!

Edit: the electrons are excited to unstable positions because of the Pauli Exclusion Principle. But why are nuclei aligning antiparallel to an external magnetic field? I dont see how PEP or any other principle comes into play here. Why are they doing that? Why not absorb the radio waves and stay aligned with the magnetic field?

Edit: Found the answer: If you apply a radio wave, this wave also has a magnetic field. The orientation of the spin will then start to precess around the new position of the field, which changes in time with the frequency of the radio wave.
« Last Edit: December 06, 2018, 04:34:08 pm by Mattjbr2 »
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ncda

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Re: VCE Chemistry Question Thread
« Reply #7696 on: December 15, 2018, 06:20:30 pm »
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Hi everyone, this is my first time asking a question on here haha. Do you think it is possible for me to achieve a 40 in Chemistry when no one at my school has ever been able to get a 40 in Chemistry? I was one of the top in my class this year in year 11 and I really love Chemistry but I am so disheartened by this fact that no one has been able to achieve a 40. Please help me. :)
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Bri MT

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Re: VCE Chemistry Question Thread
« Reply #7697 on: December 15, 2018, 06:26:26 pm »
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Hi everyone, this is my first time asking a question on here haha. Do you think it is possible for me to achieve a 40 in Chemistry when no one at my school has ever been able to get a 40 in Chemistry? I was one of the top in my class this year in year 11 and I really love Chemistry but I am so disheartened by this fact that no one has been able to achieve a 40. Please help me. :)

No one at my school hadn't gotten an A on the biology exams since it was made into one exam for the whole year rather than 1 each semester until I got 47. Similarly, all the duxes I remembered had gotten below 90 ATARs until I got 98.    I didn't get tutoring or pay for special resources either.

(Bio was my first VCE subject & I got a higher score in it which is why I mention that specifically, but I also got 40+ in chem under similar circumstances)

It is 100% possible (especially if you use these forums to help you out - I didn't when I did bio but it would have helped)
You have to be willing to work hard, and do lots of practice, but you can definitely make it :D 

ncda

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Re: VCE Chemistry Question Thread
« Reply #7698 on: December 15, 2018, 07:04:19 pm »
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No one at my school hadn't gotten an A on the biology exams since it was made into one exam for the whole year rather than 1 each semester until I got 47. Similarly, all the duxes I remembered had gotten below 90 ATARs until I got 98.    I didn't get tutoring or pay for special resources either.

(Bio was my first VCE subject & I got a higher score in it which is why I mention that specifically, but I also got 40+ in chem under similar circumstances)

It is 100% possible (especially if you use these forums to help you out - I didn't when I did bio but it would have helped)
You have to be willing to work hard, and do lots of practice, but you can definitely make it :D


Thank you very much, your experience has given me some hope haha, that's so amazing that you got 47 in Biology, I did it this year and I got a 39, I wish I had put in a bit more effort than I did but I am really glad I did it because now I understand how hard you really have to work :)
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dream chaser

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Re: VCE Chemistry Question Thread
« Reply #7699 on: December 15, 2018, 09:09:06 pm »
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Hi Guys,

Just a quick question. What is the difference in the purpose of a slit and coloured filter in colorimetry? In my text book, it does not really explain the difference. I understand that they are both in regards to allow only a particular wavelength to pass through, but do not know the exact purpose of both of them and the difference in purpose between the both of them.

All help will be much appreciated

Thanks
 :) :D
« Last Edit: December 15, 2018, 10:21:26 pm by dream chaser »

lzxnl

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Re: VCE Chemistry Question Thread
« Reply #7700 on: December 16, 2018, 01:22:27 am »
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Hi Guys,

Just a quick question. What is the difference in the purpose of a slit and coloured filter in colorimetry? In my text book, it does not really explain the difference. I understand that they are both in regards to allow only a particular wavelength to pass through, but do not know the exact purpose of both of them and the difference in purpose between the both of them.

All help will be much appreciated

Thanks
 :) :D

So, a slit works by diffraction. Larger wavelengths will diffract more, smaller wavelengths will diffract less, so only the right wavelength will be diffracted the exact right amount to hit a detector specially placed to detect that particular wavelength.

A coloured filter works by physically filtering out the colour of interest. It works by absorbing most wavelengths and only transmitting the wavelengths of interest.
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dream chaser

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Re: VCE Chemistry Question Thread
« Reply #7701 on: December 16, 2018, 06:05:59 am »
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So, a slit works by diffraction. Larger wavelengths will diffract more, smaller wavelengths will diffract less, so only the right wavelength will be diffracted the exact right amount to hit a detector specially placed to detect that particular wavelength.

A coloured filter works by physically filtering out the colour of interest. It works by absorbing most wavelengths and only transmitting the wavelengths of interest.

Okay. Thank you for the reply and help. Much appreciated

dream chaser

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Re: VCE Chemistry Question Thread
« Reply #7702 on: December 17, 2018, 06:41:43 pm »
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is the detector of a colorimeter use to record the amount of transmitted light or the absorbance of light that passes through the sample cell?

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Re: VCE Chemistry Question Thread
« Reply #7703 on: December 17, 2018, 06:47:48 pm »
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The detector of a colorimeter is used to record the amount of transmitted light.  :)
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dream chaser

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Re: VCE Chemistry Question Thread
« Reply #7704 on: December 17, 2018, 06:55:03 pm »
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The detector of a colorimeter is used to record the amount of transmitted light.  :)

Okay. But my book for some reason says it measures the absorbance

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Re: VCE Chemistry Question Thread
« Reply #7705 on: December 17, 2018, 06:58:37 pm »
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Hmmm... that's strange.

Well in a sense, it does actually measure both. I have a piece of paper from school that says it measures percentage transmission (that's where I got my info from :) ) but I guess in the same way, it does measure the absorbance since in a colorimeter they functionally do the same thing. Might be wrong though :)

Hope this helps anyway :) 
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dream chaser

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Re: VCE Chemistry Question Thread
« Reply #7706 on: December 17, 2018, 07:01:10 pm »
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Hmmm... that's strange.

Well in a sense, it does actually measure both. I have a piece of paper from school that says it measures percentage transmission (that's where I got my info from :) ) but I guess in the same way, it does measure the absorbance since in a colorimeter they functionally do the same thing. Might be wrong though :)

Hope this helps anyway :)

Okay, thanks for the help. Also, does the colour filter select the correct wavelength automatically or do people have to use trial and error to find the wavelength where the sample cell has the strongest absorbance?


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Re: VCE Chemistry Question Thread
« Reply #7707 on: December 17, 2018, 07:26:22 pm »
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Percentage absorbance and percentage transmission add up to 100% so it doesn't really matter which one is measured. Each colour corresponds to a specific wavelength of light. We know the wavelength of each colour of light on the visible spectrum so we just choose or make filters that suits our needs, so yes, by trial and error until you find a filter which transmits light of a that absorbs strongly. Btw, this isn't actually in the VCE Chemistry study design anymore.
« Last Edit: December 17, 2018, 07:28:53 pm by addict »
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dream chaser

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Re: VCE Chemistry Question Thread
« Reply #7708 on: December 17, 2018, 07:31:38 pm »
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Percentage absorbance and percentage transmission add up to 100% so it doesn't really matter which one is measured. Each colour corresponds to a specific wavelength of light. We know the wavelength of each colour of light on the visible spectrum so we just choose or make filters that suits our needs, so yes, by trial and error until you find a filter which transmits light of a that absorbs strongly. Btw, this isn't actually in the VCE Chemistry study design anymore.

Okay, thank you for the reply.However, doesn't colorimetry fall under chemical analysis which is in Unit 3?

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Re: VCE Chemistry Question Thread
« Reply #7709 on: December 17, 2018, 07:40:21 pm »
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I just finished the 3/4 course this year and as far as I can remember, as of 2017, instrumental analysis only includes NMR, IR spectroscopy and chromatography (HPLC only, not including thin layer and  gas chromatography). Can someone else confirm? You could also double check in the study design. I'm pretty sure instrumental analysis is in Unit 4 now.
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