# postlab 7.docx - Spectrophotometric Determination of Iron...

• 5

This preview shows page 1 - 4 out of 5 pages.

Spectrophotometric Determination of Iron in Mohr’s Salt with Phenanthroline Post Lab Quantitative observations Mass of a weighing paper (or dish) 0.5151 g Mass of a weighing paper (or dish) and Mohr’s salt 0.5432 g Mass of Mohr’s salt 0.0281 g The concentration of Mohr’s salt in 250 mL volumetric flask: 2.87 x 10 -4 M Mass of Mohr’s salt : 0.5151 g – 0.5432 g = 0.0281 g Concentration of Mohr’s salt in 250 mL volumetric flask : = n/V = 0.0281g / 392.16 g/mol / (250 mL / 1000 mL) = 2.87 x 10 -4 M Standar d The volume of Stock Solution, mL Concentratio n Absorbance Averaged Absorbanc e y-error Trial 1 Trial 2 Trial 3 #1 5.00 1.44 x 10 -5 M 0.20 0.20 0.19 0.20 0.0058 #2 10.00 2.87 x 10 -5 M 0.35 0.33 0.34 0.34 0.010 #3 20.00 5.74 x 10 -5 M 0.54 0.55 0.55 0.55 0.0058 #4 30.00 8.61 x 10 -5 M 0.68 0.70 0.71 0.70 0.015 #5 40.00 1.15 x 10 -4 M 0.82 0.84 0.83 0.83 0.01
#6 50.00 1.44 x 10 -4 M 0.92 0.91 0.91 0.91 0.0058 Slope: 5457.9 R 2 value: 0.9672 0 0 0 0 0 0 0 0 0 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 f(x) = 5457.9 x + 0.18 R² = 0.97 Calibration curve Concentration (M) Averaged Absorbance Absorbanc e reading of the unknown in 100 mL volumetric flask Trial 1 Trial 2 Trial 3 Averaged Absorbanc e 0.49 0.52 0.48 0.50 Averaged Concentration of the unknown solution in 100 mL volumetric flask: 5.808 x 10 -5 M
Original concentration of the unknown solution: 1.452 x 10 -4 M Calculation: