Aas & Nuclear Chemistry ???? (1 Viewer)

[tristambrown]

Just a few quick questions

For AAS - Is the calibration curve a

A: Curve of best fit (misses points and forms nice algebraic curves)

or

B: a Linear straight line that passes the points (or as close to them as possible without bending the line)


Also we dont need to know why specific wavelengths are emitted & absorbed by elements do we(like all the excitation energies etc?); Just that the signature of each is unique to that element and that this phenomena is used in aas to measure amount of light absorbed (not recieved from a known quantity sent through the flame) at the detector, right ???


For graphs (In general):

If we dont have values all the way down to 0 do we still draw the graph all the way to the axis ???? .. is this true for standars graphs aswell as calibration curves ?


For Nuclear chemistry:

Unstable isotopes
- N ratio too high---Beta Decay--- Beta emitter + forms extra proton
- P:N ratio too high ---Beta Decay--- Beta emitter + forms neutron
- Mass too high ----- Alpha emitter ---- Helium 2protons mass 4 spat out

Do we need to know what "too high" is .. excel seems to simply state that it is uinstable when it;s energy level is "too high" and is stable when it's energy level is too low to allow it to emit radiation.

I have read N ratio values here and am concerned that we need to know values ?? anyone know A if we need to know values or b: how to calculate the values required

Thanks all

 

[tristambrown]

BUMP

Ive searched both my chem text books and cant find anything conclusive for AAS graphs .. Both seem to have straight line graphs but then the values they are giving to graphy are all in a straight line anyway so it is in no way conclusive ...

the search continues ...

 

[Harry Seacombe]

I'm pretty sure it's a line of best fit. Chances are if we get a graph to do, there'll be one outlier point. If you ignore it, you should be right. However, I'm not 100% sure.

 

[Naylyn]

We don't have to know about AAS calibration curves, the syllabus says:
"describe the use of AAS in detecting concentrations of metal ions in solutions and assess its imact on scientific understanding of the effects of trace elelments"

I dont see how they could possibally get calibration curves or specific wavelengths, anyway real chemists don't have to remember specific wavelengths why should we?

I do believe that when there are too many protons it becomes a positron emitter, ie it emits a positive beta.

I have found that the best tool for working out whether an atom is stable or not is the periodic table since it gives generally gives values for the most common stable isotope, you can see that if the isotope given varies greatly from the periodic table value it is most likely unstable.

I don't think they can expect us to know specific values for N they would have give us a graph that shows the band of stability if they wanted us to work out if an isotope was stable or not based on a specific value for N.

 

[tristambrown]

thnaks for that guys ...

re the curves - i more expect them to give us a data set and ask us to find a valud from that ...

eg i am expecting a q like the following if there is one:

A sample x containing <insert random element here> from a river was taken and analysed along with known sample concentrations

DATA
absorbance ......ppm
5ppm:0.2
Xppm0.04
15ppm:0.06
20ppm:0.08


Draw the Calibration curve for the dataset and from this estimate the concentration of <insert random substance> in sample X ... i just dont want to lose a mark for drawing a curve when a line was expected or for extending the line/curve to 0 when we werent supposed to or vice versa (for each case)

 

[dral]

As far as the neutron/proton ratios, it's not all that specific, but it usually starts of in the early elements with something between 1-1.25 and then curves up to somewhere around 1.5 for heavier elements. They'd give you a graph or something really obvious. If not, then don't stress it because nobody else got it right either.