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Ultraviolet/Visible (UV-Vis) Spectroscopy of Potassium PermanganatePowerPoint Presentation

Ultraviolet/Visible (UV-Vis) Spectroscopy of Potassium Permanganate

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### Ultraviolet/Visible (UV-Vis) Spectroscopy of Potassium Permanganate

### Special Thanks nm

By Robert Bohman

November 4th 2006

CH EN 4903

Importance to industry Permanganate

- Potassium Permanganate is used to kill bacteria in reclaimed water
- Use UV-Vis to ensure that the concentration of Potassium Permanganate is at acceptable limit

Overview Permanganate

- Theory
- Light Absorption Spectrum
- Experimental Procedure
- Results
- Conclusion
- Q & A

THEORY Permanganate

Properties of Light Permanganate1

- c = λν c = speed of light in vacuum (2.998 x 108 m/s)
λ = wavelength (m)

v = frequency (Hz)

- E = hc/ λ = hcv` h = Planck’s constant (6.626 x 10-34 J•s)
v` = wavenumber (m-1)

Understanding Beer’s Law Permanganate2

- Transmittance T = P/P0
Schematic of Single-Beam Spectrophotometer, P0 is the irradiance entering sample, P is the irradiance leaving sample, and b is pathlength2

P = irradiance (energy per unit area of light beam)

Understanding Beer’s Law Permanganate3

- Absorbance A = log (P/P0) = -log (T)
- Beer’s Law A = εbc
ε = molar absorptivity (M-1 cm-1)

b = pathlength (cm)

c = concentration (M)

LIGHT ABSORPTION SPECTRUM Permanganate

Absorption Spectrum of Light Permanganate4

EXPERIMENTAL PROCEDURE Permanganate

Detecting Potassium Permanganate Permanganate

- Potassium permanganate (KMn04) in solution is purple / violet color meaning maximum absorption should be at 500 – 550 nm
- Prepared 5 known concentrations of KMnO4: 1ppm, 20ppm, 40ppm, 60ppm, 80ppm

Detecting Potassium Permanganate Permanganate

- Calibration Standards measured first on a Perkins-Elmer Lambda 35 over entire UV-Vis region to determine max absorption
- KMnO4 absorbed best at ≈ 520 nm
- A Bausch & Lomb Spectronic 21 was used to make all measurements

RESULTS Permanganate

Calibration Curve for KMnO nm4 using UV-Vis Spectroscopy, Absorption vs. Concentration

Determination of Unknown Concentration of KMnO nm4

- Used cuvette of 1cm length
- ε = slope of line = 0.029 ppm-1 cm-1
- Unknown #4 concentration found using
c = A/0.029

- 36 ppm = 0.462 %A / 0.029 ppm-1

Error Analysis nm

- Used 10.00 ± 0.05mL volumetric pipette to make all solutions
- Measured density of water with:
= (999.8392 + 16.945176t – 7.9870401*10-3t2 – 46.170461*10-6t3 + 105.56302*10-9t4 – 280.54253*10-12t5)/(1 + 16.879850*10-3t)5

- H2O = 0.997883 g/mL at 21.5°C
- Measured accuracy of scale to be 0.0005g

Error in Unknown nm

- Errors determined graphically from calibration curve
- A = ± 0.01%
- Concentration = ± 1.00 ppm
- Final concentration of Unknown #4 was
36 ± 1.00 ppm

CONCLUSION nm

Conclusion nm

- How accurate are results?
Can be determined by R2 value for slope of calibration curve.

For this example R2 = 0.999

Conclusion nm

- Use Beer’s law to determine concentration of unknown concentration
- Find the molar absorptivity through the slope of calibration curve
- Determined ε = 0.029 ppm-1 cm-1
- Determined Unknown #4 concentration to be 36 ± 1.00 ppm

Q & A nm

To Triston Thorpe and Jason Judkins in helping with the experiment

References nm

- Harris, Daniel C. Sixth Edition Quantitative Chemical Analysis. Pg. 408-409. New York: W.H. Freeman and Company, 2003.
- Harris, Daniel C. Sixth Edition Quantitative Chemical Analysis. Pg. 410. New York: W.H. Freeman and Company, 2003.
- Harris, Daniel C. Sixth Edition Quantitative Chemical Analysis. Pg. 411-412. New York: W.H. Freeman and Company, 2003.
- Harris, Daniel C. Sixth Edition Quantitative Chemical Analysis. Pg. 413. New York: W.H. Freeman and Company, 2003.
5. CRC Handbook of Chemistry and Physics. Pg. F-6. Cleveland, Ohio: The Chemical Rubber Co., 1968.

Relax nm

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