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Spectrophotometric determination of iron with 1,10-phenanthroline.

Goals:
To become familiar with basic methods in UV-Visible molecular absorption spectrophotometry for quantitative chemical analysis.

Objectives:
Obtain absorption spectrum of the tris(1,10-phenanthroline)iron(II) complex and determine the analytical wavelength Determine percent iron in a solid sample
absorption of light Absorption of Light: Beer-Lambert Law: A = bc

Procedure:
Obtain absorption spectrum of complex and determine max
Prepare working stock solutions
-Standard Fe from pure Fe(NH4)2(SO4)2.6H2O (Mohr’s salt)
-Stock unknown solution
Weigh 0.2 g solid unknown, dissolve in dilute acid and dilute to 500 mL
Prepare standard and unknown solutions.
To 100-mL volumetric flasks add
-5 mL pH 5 buffer
-5 mL 10% NH2OH.HCl
Aliquots of std Fe or unkown
include a blank solution with no Fe
-10 mL of 0.02 M 1,10-phenanthroline
-Dilute to volume and measure absorbance at max
Construct Beer’s Law Plot (A vs c) and calculate %Fe in original solid sample.
-Typical results are 5 to 15% Fe. Report to nearest 0.01% Fe.

Calculations:
You want to report %Fe in your solid sample, so you need to find the mass of Fe in your weighed sample. Here is a general outline of the approach.
Preparation of your stock sample solution.
-You weighed x.xxxx g of your solid unknown.
-You dissolved it in dilute acid and diluted it to yyy.y mL to prepare your stock sample solution.
---Your stock sample solution contains all of your solid sample. If you can determine the molar concentration of Fe in this solution, you can calculate the mass of Fe in your sample.
Your calculated concentrations are based on the absorbances of your prepared standards and your prepared unknown.
-Prepared standards.
---Based on the mass of pure Fe(NH4)2(SO4)2.6H2O, and the dilutions you did, you compute the concentrations of Fe (mol/L) in your calibration standards.
---You measure the absorbance of each standard and construct a calibration curve.
-Prepared unknown (the one for which you measured the absorbance)
---From the calibration curve, you determine the concentration of Fe (mol/L) in your prepared unknown.
---Based on the concentration of Fe in your prepared unknown, and the dilutions(s) of the stock sample solution you performed to prepare that standard, you compute the molar concentration of Fe in your stock sample solution.
--Now you can calculate the amount of Fe in your unknown sample.


when you want to buy 1,10-Phenanthroline,please contact us
Email:whcind@126.com

    
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