ATAR Notes: Forum

VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: ggxoxo on March 15, 2012, 08:43:55 pm

Title: AAS
Post by: ggxoxo on March 15, 2012, 08:43:55 pm

Hey guys,

What effect on the calculated concentration if in AAS a calibration curve was not used (i.e. higher, lower, same as true value)?

Wouldn't it just be the same as the true value?

Also the flame in the atomiser is not allowed to excite the electrons right?

Sorry last question: why is the cathode in the lamp made of the same metal as the element to be determined?
A- The energy emitted by the lamp is exactly the same amount required by the atoms to be excited
B- The energy emitted by the lamp is more easily absorbed by the atoms to be excited

The answer is A. Why?

Title: Re: AAS
Post by: jaydee on March 16, 2012, 10:42:10 pm

if a calibration curve wasnt used you would have no idea of what to compare it to.
Atomiser flame simply converts the sample into atomic vapour/ into its free atoms. Energy is insufficient to excite electrons of the metal
The cathode lamp is made out of the same element as the chemical under analysis so it can provide the exact amount of energy or wavelength to excite electrons. option B refers to the function of the atomiser flame since the atomiser flame gives a narrower absorbance, hence much more accurate analysis

Title: Re: AAS
Post by: ggxoxo on March 17, 2012, 09:04:50 pm

Quote from: jaydee on March 16, 2012, 10:42:10 pm

if a calibration curve wasnt used you would have no idea of what to compare it to.

so is it lower/higher/same? The answer as I recall was lower; but since a calibration curve is only a comparison and if you don't have a comparison it could be lower/higher right?

Thank you for your other answers as well!!! Really appreciate it!

Title: Re: AAS
Post by: ggxoxo on March 17, 2012, 09:08:52 pm

Quote from: ggxoxo on March 15, 2012, 08:43:55 pm

Sorry last question: why is the cathode in the lamp made of the same metal as the element to be determined?
A- The energy emitted by the lamp is exactly the same amount required by the atoms to be excited
B- The energy emitted by the lamp is more easily absorbed by the atoms to be excited

The answer is A. Why?

Also I don't get the difference between the options; can you please explain it?

Title: Re: AAS
Post by: jaydee on March 18, 2012, 06:25:23 pm

well im not really sure about the calibration curve one since the only questions ive come across have been all about the calibration curve. The diff between A and B is that the cathode lamp is made out of the same element as the sample under analysis so it can provide very specific wavelengths that only the sample will absorb/excited. A and B do sound similar but usually its about the best answer in multi choice so itd be A. B is too vague since it could refer to the atomiser flame  (since itsfunction is to give a narrower absorbance)

Title: Re: AAS
Post by: ggxoxo on March 19, 2012, 04:49:53 pm

Quote from: jaydee on March 18, 2012, 06:25:23 pm

well im not really sure about the calibration curve one since the only questions ive come across have been all about the calibration curve. The diff between A and B is that the cathode lamp is made out of the same element as the sample under analysis so it can provide very specific wavelengths that only the sample will absorb/excited. A and B do sound similar but usually its about the best answer in multi choice so itd be A. B is too vague since it could refer to the atomiser flame  (since itsfunction is to give a narrower absorbance)

OMG I totally forgot about picking the best answer!!! Thanks for that jaydee! I really appreciate your help. THANK YOU :)