An aliquot of 3.0 mL was taken out from the reaction mixture
at regular time intervals and the absorbance was measured
spectrophotometrically at kmax = 560 nm. It was observed
that the absorbance of the solution decreases with increasing
time intervals, which indicates that the concentration of RB
decreases with increasing time of exposure. A plot of
2+ log A versus time was linear and follows pseudo-firstorder
kinetics. The rate constant was measured using the following
expression: