Chemistry 2210A/B Lecture Notes - Lecture 2: Rayleigh Scattering, Joule, Photon
12 Dec 2017
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E and "wave length" have an inverse relationship: as the wavelength gets shorter, the photon energy increases. For convenience, we can calculate the product hc on a molar basis. If the wavelength is expressed in nanometers then hc=119627 kj mol ^-1 hc= 6. 626 x10 ^-34 j/s x 2. 998x10^8 ms^-1 x 6. 023 x10^23 mol^-1. = 0. 119627 mjmol^-1 divide by 10^3 =1. 119 x 10^-4 mkj mol ^-1 divide by 10^-9 = 119627 nmkjmol ^-1 therefore hc= 119627 nmkjmol ^-1. Effects of absorption of light on molecules in various spectral regions. Infrared (ir: probing vibrational structure, visible (vis) If the molecule absorbs photons in the visible stage, now the electrons will be probed: probing electron structure, promote electrons between orbitals, ultraviolet (uv, break bonds. * rayleigh scattering is why the sky is blue * Energy of photon with wavelength = 280 nm: e = 119627 nm kj mol^-1 /280 nm, = 427 kj mol^-1, uvc - uvb overlap.
