University of Washington

• CHEM 453'

• University of Washington - Department of Chemistry Chemistry 453 Homework Assignment 10 Problem 1 The longest wavelength absorption band of chlorophyll a occurs at 680 nm. a. Calculate the energy of a photon of that wavelength in J, eV and kJ/Einstein a) x J photon x m hc x Jxsx x m s E 2.92 10 / 6.8 10 6.62 10 3 10 / 19 7 34 8 − − − Δ = = = λ 2.92x10 J / photonx1eV /1.602x10 J 1.82eV / photon 19 19 = = = − One Einstein corresponds to one mole of photons, so the energy per Einstein is: 2.92x10 J / photonx6.02x10 photon / Einstein 175.8x10 J / Einstein 19 23 3 = = − Problem 2 The molar extinction coefficient of benzene is 100 at 260 nm, Assume this number is independent of solvent. a. What concentration would give an absorbance of 1.0 in a 1 cm cell? b. What concentration would allow only 1% of the 260-nm light to be transmitted through a 1 cm cell? c. If the density of liquid benzene is 0.8 g/cm3, what thickness of benzene would give an absorbance of 1 at 260 nm? a) C A l M2 / 1/(100)(1) 10− = ε = = b) log log0.01 2 0 ⎟ = − = ⎠ ⎞ ⎜ ⎝ ⎛ = I I A C x M2 2 10− = c) The concentration of pure benzene is: 0.8g / cm x1,000cm / lx1mole / 7.8g 10.3M 2 3 = l A C x cm 4 / 1/(100)(10.3) 9.8 10− = ε = = Problem 3 Consider the Schrodinger equation and its solution f