Light attenuation: Using the Beer-Lambert Law: a) Plot (Ix/Io), versus path length in centimeters, for a 1.

Light attenuation: Using the Beer-Lambert Law:

a) Plot (Ix/Io), versus path length in centimeters, for a 1.0 x 10-3 M solution of an absorber in a 10-cm long cell, with a molar absorptivity of (i) ε = 1.0 x 101 L cm-1 mol-1 , (ii) ε = 1.0 x 102 L cm-1 mol-1 and(iii) ε = 1.0 x 103 L cm-1 mol-1 . (5 marks)

b) In each case also calculate the path length at which the irradiation intensity would have dropped to 50% of its initial value. Use this result to illustrate why rapid stirring is desirable in photochemical reactions involving highly absorbing solutions. (5 marks) Hint: Use a spreadsheet, solving for (I/Io) at 100 evenly-spaced lengths along the path of the beam in steps of 0.1 cm.