You have a stock solution of a food-coloring dye that is 0.0500 M
CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
You have a stock solution of a food-coloring dye that is 0.0500 M. A laboratory protocol requires you to prepare 100.0 mL of a working solution such that, after a further 1:10 dilution (one part working solution to nine parts water), the final sample will exhibit an absorbance of 0.600 when measured in a 1.00 cm cuvette at 620 nm. At this wavelength the molar absorptivity of the dye is 2.40×103Lmol−1cm−1.
(a) Calculate the molarity that the final (post-dilution) sample must have to give an absorbance of 0.600 under the stated conditions.
(b) Determine the molarity required for the 100.0 mL working solution before the 1:10 dilution is carried out.
(c) Compute the exact volume of the 0.0500 M stock solution that must be transferred into the 100.0 mL volumetric flask to prepare the working solution calculated in part (b). Express your answer to the appropriate number of significant figures and include units.
(d) Outline a step-by-step laboratory procedure that would allow another student to reproduce this working solution with minimal systematic error.