Three unknown solutions were prepared by pipetting 5 mL of an unknown nickel sol
ID: 913520 • Letter: T
Question
Three unknown solutions were prepared by pipetting 5 mL of an unknown nickel solution into a 250 mL volumetric flask and diluting to the mark. Then three samples were prepared from this dilute unknown solution by pipetting 15 mL of the dilute solution into a 200 mL flask, to which the reagents were added then it was diluted to the mark. The resulting solutions were analyzed by UV Spectroscopy and the unknown absorbance value were converted to concentration by means of calibration curve, Table 4 - 1. Fill in the diagram with appropriate volumes. Determine the concentration of the original nickel solution, in ppm Ni, from each of the three unknown solution and an average. Included appropriate error calculations. Show complete calculations using Trial 1 data. Present results for all trials and average with uncertainties.Explanation / Answer
Diagram,
Unknown (flask) --- Take 5 ml ----- diluted to 250 ml (flask) ------Take 15 ml of diluted sample ----- Diluted to 200 ml (flask)
Calculation for Trial 1.
Ni concentration in 200 ml of diluted sample = 12.589 +/- 0.859 ppm
Ni concentration in 15 ml of original diluted solution = 12.589 +/- 0.859 ppm
Ni concentration in 5 ml of original diluted solution = (250/15) x 12.589 = 209.82 +/- 0.859 ppm
Results,
Ni concentration in original sample = 209.82 +/- 0.859 ppm [with value - uncertainty - unit]
Similarly, Ni concentration in Trial 2 = 220.57 +/- 0.967 ppm [with value - uncertainty - unit]
and, Ni concentration in Trial 3 = 214.98 +/- 0.894 ppm [with value - uncertainty - unit]
Average Ni concentration = 215.12 +/- 1.3 ppm [with value - uncertainty - unit]
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