Experiment 33 Colorimetric Determination of Iron CHE1181

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 determine the concentration of %Fe in the unknown sample CHE1182

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 CHE1183

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 CHE1184

Spectrophotometer (Parts A and B) An instrument that will indicate the amount of light (of one wavelength) absorbed by a sample CHE1185 LED readout readout detector sample monochromator Light source slit

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 CHE1186

Calibration Curve CHE1187 Concentration, mg Fe / mL (x10 -3 ) Absorbance

Using the Calibration Curve to Find Concentration of the Unknown Solution CHE1188 Show this on your graph Absorbance Unknown solution absorbance reading Concentration of unknown solution Concentration, mg Fe / mL (x10 -3 )

For All Students Typing error on x axis of graph paper: mg Fe / mL (x ) Typing error on y axis; should be Absorbance Calculating % Fe in unknown sample: CHE1189

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: 1.grams converted to mg 2.mg divided by size of first volumetric flask, in mL 3.1 mL diluted by size of second volumetric flask, in mL CHE11810