# 4 line the seven flasks in order blank the 5 25 ml

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4. Line the seven flasks in order; blank, the 5-25 mL iron stock solutions, and the unknown solution. Then add the following. a. 1ml of the hydroxylamine solution b. 8ml of the sodium acetate c. Then add phenanthroline till the solution turns a dark orange 5. Swirl each flask to mix the contents, then carefully dilute each solution with distilled water to the 100mL mark and mix thoroughly. 6. Allow the solutions to stand for 15 minutes to fully develop the color. Once developed, the color is stable for hours. 7. Measure the absorbance for the 2.5 ppm solution at wavelength from about 400 to 700 nm. Take readings at 25nm intervals except near the vicinity of the absorbance maximum, where you take the readings at 5 or 10 nm intervals. Find out the maximum absorption wavelength. 8. Measure the absorbance of each of the four standard solutions at the macimum absorption wavelength. Measure the unknown in the same way. 9. Plot the absorbance against the wavelength using the 2.5 ppm solution. Results: Molar Absorbtivity = ε
C= 4.477x10 -5 M; b= 10mm; A= 1.00 Since the equation of the line is approximately y=0.03x-0.0065 we can calculate the concentration of a solution with an absorbance of 0.2. Conclusion: By using Beer's law we determined the molar absortivity to be . Then plotting the standard solutions on a calibration curve and finding the trend line, a concentration of the unknown was calculated to be 0.236ppm.
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