Problems
(1) (a) Convert the following percent transmittances to absorbance:
(b) Convert the following absorbances to transmittance:(2) The concentration of a liquid sample contained in an infrared cell of thickness 0.15 μm is 0.5 M.
Calculate the molar absorptivity of the sample if the absorbance at a specified wavenumber is 0.300.
(3) A solution of concentration x molar absorbs 70% of the radiation passing through it. If Beer's law is
obeyed, what percentage of radiation would be transmitted at a concentration of x/3 molar?
(4) A solution containing 3.0 ppm of an analyte (m.w. = 155) has a transmittance of 65.0% in a 1 cm
cell. Calculate:
(a) the absorbance of the solution;(b) the absorbance and percent transmittance for a solution containing 5.2 ppm of the analyte;(c) the molar absorptivity of the analyte.(5) Ti and V can be determined simultaneously in steel as their coloured peroxide complexes. 1 mg of
each metal in 50 cm^3 of solution gave the following absorbances:
Two steel samples, dissolved in 50 cm^3 , each 1.000 g, gave the following absorbances:
Calculate the percentage of Ti and V in each sample.
(6) The absorption characteristics of solutions of the acid–base indicator methyl red at two wavelengths
were:
What is the acid dissociation constant of methyl red?
(7) To take account of stray light in spectrophotometric measurements, the true absorbance values
should be calculated using the formula: