15. Garrett and Carper (J. Am. Pharm. Assoc. Sci. Ed. 44, 515, 1955) determined the zero-order rate constant for the degradation of the colorants in a multisulfa preparation. The results obtained at various temperatures are as follows: °C ko (h-¹) 40 0.00014 50 0.00031 60 0.00079 70 0.00183 a) Plot these results according to the Arrhenius relationship and compute the activation energy, Ea. b) Extrapolate the results to 25°C to obtain ko at room temperature. You can also use regression analysis to answer a) and b). c) The rate of decrease of absorbance of the colored preparation at a wavelength of 500 nm was found to be zero order and the initial absorbance, AD, was 0.470. This preparation should be rejected when the spectrophotometric absorbance, A, falls to a value of 0.225. Therefore, to predict the absorbance of the preparation at any time t hours after preparation, one uses the zero-order equation A-A-kot. Calculate the predicted life of the preparation at 25 °C.

Fig: 1