It is possible, although less accurate, to do a standard addition with only one sample. An unknown Fe sample was analyzed by AAS and gave an absorbance reading of 0.160. To the same sample we added 1.5ppm Fe and the new absorbance reading was 0.205. Calculate the ppm of the unknown Fe.
Could someone please explain to me on how to do this question step by step. Thanks.
You could probably set up a proportion.
so....
0.160/x= 0.205/1.5ppm
Solve for x.
I agree it probably can be done with a proportion; however, I wouldn't set up the proportion that way.
0.160 is for x
0.205 is not for 1.5 ppm but for 1.5 ppm+xppm.
(0.160/x) = (0.205/1.5+x) and solve for x.
Another way.
0.205 = 1.5 + x
0.160 = ......x
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0.045absorbance due to 1.5 ppm
Then 1.5 ppm x 0.160/0.045 = ?
To calculate the ppm of the unknown Fe, we need to use the standard addition method. This method involves adding a known amount of the element of interest (Fe in this case) to the unknown sample and measuring the change in absorbance. Here's how you can solve the problem step by step:
Step 1: Calculate the change in absorbance:
Change in absorbance = Absorbance with standard - Absorbance without standard
Change in absorbance = 0.205 - 0.160 = 0.045
Step 2: Convert the change in absorbance to concentration:
We know that we added 1.5 ppm of Fe to the unknown sample. Therefore, 1 ppm of Fe gives a change in absorbance of 0.045.
Concentration of added Fe = Change in absorbance / Absorbance per ppm
Concentration of added Fe = 0.045 / (1 ppm Fe) = 0.045 / 1 = 0.045 ppm
Step 3: Calculate the concentration of the unknown Fe:
The concentration of the unknown Fe can now be calculated by subtracting the concentration of the added Fe from the concentration of the final absorbance.
Concentration of unknown Fe = Final absorbance - Concentration of added Fe
Concentration of unknown Fe = 0.205 - 0.045 ppm = 0.16 ppm
So, the ppm of the unknown Fe is 0.16 ppm.