1. Quantitative Chemical Analysis Seventh Edition Quantitative Chemical Analysis Seventh Edition Chapter 18 Fundamentals of Spectrophotometry Copyright © 2007 by W. H. Freeman and Company Daniel C. Harris

2. Light has: Intensity Color (wavelength) Polarization

3. Intensity

4. Transmittance Absorbance

5. Transmittance Absorbance Beer’s Law

6. ε = 313 M -1 cm -1 b = 2 cm T = 3.16% = 0.0316 A = -logT = 1.50 c = 1.5/(313 M -1 ) (2 cm -1 ) = 0.0024 M

8. dP(x)/dx = -κ P(x)  P(x) = exp(-κ x)

10. Beer’s law

11. Molar extinction Coefficient ~250 L.mol -1 cm -1 Cross section ~10 -18 cm 2

22. Absorption of a mixture

23. Isosbestic point

24. (wavelength) x (frequency) = speed [m/s] λν = c [10 8 m/s]

27. 436 nm  what frequency?

29. Visible spectrum

30. Your Eyes See the Color that is NOT Absobed

31. Hexaquotitanium (III) Solutions Appear Violet Due to Absorption of Yellow and Green Light

32. Subtraction of Light by Absorption Leads to Color you See

35. What makes a molecule absorb light?

37. Electron motion (fs)  resonant frequency ~ 300 nm UV-VIS ~ 10 -15 s  ν ≈ 10 15 s -1

38. What makes a molecule absorb light? Electron motion UV-VIS excites electrons!

39. E = h ν

45. Electron diffraction pattern from a beryllium atom

46. What makes a molecule absorb light? Nuclear motion ~ 3000 nm infrared

47. What makes a molecule absorb light? Nuclear motion ~ 300,000 nm microwave

48. What makes a molecule absorb light? Oscillating DIPOLE moment

49. What makes a molecule absorb light?

51. green house gas http://science.widener.edu/svb/ftir/ir_co2.html

52. What makes a molecule absorb light? [cm -1 ] = 1/λ = ν/c =E/hc

53. What makes a molecule absorb light? 3200 cm −1 broad, strong O-H stretch (alcohols) 3000 cm −1 broad, medium O-H stretch (carboxylic acids) 1200 cm −1 strong, O-H bending 2800 cm −1 strong, C-H stretch 1400 cm −1 variable, C-H bending 1700 cm −1 strong, C=O stretch 1200 cm −1 strong, C-O stretch

54. What makes a molecule absorb light?

56. E = h ν