SOLVE # 29 In order to measure the amount o\' Zn in hair using an atomic absorpt
ID: 981000 • Letter: S
Question
SOLVE # 29
In order to measure the amount o' Zn in hair using an atomic absorption instrument Shelby needs to prepare a calibration curve of atomic absorbance for five solutions cf known Zn concentration. For each concentration 100 mL of solution is needed and the standards need to be in the 0.4 - 1.6 ppm Zn rançe. The available Glassware is listed in Q1 ard a 1000 ppm Zn primary standard solution is available. Table 2 Capacity and Tolerance of Available Graduated Cylinders, Volumetric Flasks and Ptpattas Which glassware would be the best to use to prepare the calibration standards? Oescnse how you would make five calibration standards in the 0 4-1.6 oprr range staring with the 1000 pprr Zn primary standard solution. Explain, using complete sentences, why the glassware chosen for this problem is the best o4 those listed in Table 2.Explanation / Answer
a) for volumentric measurements we always prefere to use volumetric flasks. These are used for precise measurement of solution during their preparations
b) As mentioned we have 1000 ppm of Zn primary standard solution
first we will dilute the given standard as follows
we will take 10mL of above solution (pipete) and will fill it in 200mL of volumetric flask
(Concentration X volume )initial = (concentraion x volume ) final
1000 X 10 = concentration X 200
Concentration = 50 ppm
First
(i)
Again we will dilute the solution to 1.6ppm
(Concentration X volume )initial = (concentraion x volume ) final
50 X volume = 1.6 X 100
Volume = 3.2 mL
So we will take 3.2 mL of 50ppm solution and dilute it in 100mL of volumetri flask.
We can measure 3.2 mL from volumetric pipet
Let we will prepare the following 4 standards
(ii) 1.2
(Concentration X volume )initial = (concentraion x volume ) final
1.6 X Volume = 1.2 X 100
Volume = 75mL
So we will measure 75 mL of solution with the help of pipet and will dilute it to 100mL by the help of volumetric flask
(iii) 1.0
(Concentration X volume )initial = (concentraion x volume ) final
1.2 X Volume = 1 X 100
Volume = 83.3 mL
(iv) 0.8
(Concentration X volume )initial = (concentraion x volume ) final
1.6 X Volume = 0.8 X 100
Volume = 50mL
(v) 0.4
(Concentration X volume )initial = (concentraion x volume ) final
0.8 X volume = 0.4 X 100
Volume = 50mL
c) these are the glasswares which are precised and standard for measurement for the volumetric estimations
These appratus are calibrated to give the accurate volumes.
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