Colorimetric Determination of Iron Experiment 33 Colorimetric Determination of Iron CHE118

In Lab Work in groups of 4 2 people do part A; preparing the standard solutions 2 people do part B; preparing the 3 trials of the one unknown sample Everyone makes their own calibration curve and determines the concentration of %Fe in the unknown sample CHE118

Part A Prepare all solutions at the same time Prepare a blank solution (no Fe) Allow only 15 minutes for color development Use disposable test tubes instead of cuvettes for use in the spectrophotometer CHE118

Part B Prepare all solutions at the same time Follow some of Part A procedure (no Fe) Share the blank solution (no Fe) from Part A Allow only 15 minutes for color development Use disposable test tubes instead of cuvettes for use in the spectrophotometer CHE118

Spectrophotometer (Parts A and B) An instrument that will indicate the amount of light (of one wavelength) absorbed by a sample readout detector sample monochromator Light source slit LED readout CHE118

Making the Calibration Curve You will acquire an absorbance reading for each standard solution prepared (share data) Use the data from Part A to construct the calibration curve CHE118

Calibration Curve Concentration, mg Fe / mL (x10-3) Absorbance CHE118

Using the Calibration Curve to Find Concentration of the Unknown Solution Absorbance Unknown solution absorbance reading Concentration of unknown solution Concentration, mg Fe / mL (x10-3) Show this on your graph CHE118

For All Students Typing error on x axis of graph paper: mg Fe / mL (x 10 -3) Typing error on y axis; should be Absorbance Calculating % Fe in unknown sample: CHE118

mg/mL of original sample You will know the grams of original sample from the balance readout, and you will know the dilutions made during sample preparation: grams converted to mg mg divided by size of first volumetric flask, in mL 1 mL diluted by size of second volumetric flask, in mL CHE118