.V.-VisIbl I) What is the energy in electron volt (eV), of U.V. radiation at 250

Question

.V.-VisIbl I) What is the energy in electron volt (eV), of U.V. radiation at 250 nm., and also of Visible II.) What is meant by "Quantization" in Spectroscopy? III) Describe and Explain the four possible electronic transitions in U.V. Spectroscopy IV.) What is the difference between a photometer and a spectrometer? V.) What are the criteria for selecting a wavelength for a specific analysis in UV.-Visible radiation at 550 nm. [ Show all clculations.] Absorption Spectroscopy? Vi.) What are the effects of conjugation and aromaticity on UV-Vis absorption spectroscopy ?

Explanation / Answer

1.

(a) UV radiation

Energy = Planck's constant * speed of light / wave length

E = 6.626 * 10-34 * 3.0 * 108 / ( 250 * 10-9 )

E = 7.95 * 10-19 J

But,

1 eV = 1.602 * 10-19 J

Then,

1 J = 1 / (1.602 * 10-19) eV

Therefore,

E = 7.95 * 10-19 / ( 1.602 * 10-19)

E = 4.96 eV

(b) For Visible radiation,

Energy = Planck's constant * speed of light / wave length

E = 6.626 * 10-34 * 3.0 * 108 / ( 550 * 10-9 )

E = 3.61 * 10-19 J

But,

1 eV = 1.602 * 10-19 J

Then,

1 J = 1 / (1.602 * 10-19) eV

Therefore,

E = 3.61 * 10-19 / ( 1.602 * 10-19)

E = 2.25 eV

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