Question

Absorbance Concentration (M) Dilution # 1 .79 S.000e-4 M Dilution #2 .54 3.750e-4 M Dilution #3 .31 2.500e-4 M ilution #4 .11 1.250e-4 M Construct a plot of absorbance (y-axis) versus concentration (x-axis) from the data above. Determine the slope of the best-fit line. Make sure to force the best fit straight ine through the origin. Excel has an option to do this (instructions.for Excel 2013.on Windows, instructions.for Excel.2011 on Mac) >Submit your answer to this question to the correct number of significant figures, but carry forward all the digits of your calculated answer for use in following calculations The molar absorptivity constant is 1.5x10 Your results are now shown above. Please use 1.SE+3 as your molar absorptivity constant in the subsequent calculations below Question #2 Here are your data for the Commercial Aspirin CA1 sample solutions Mass Absorbance mmercial Aspirin CA1 0.1620 g .37 Part 1: Determine the concentration of salicylic acid in the Commercial Aspirin CA1 sample solution. ->Submit your answer to this question to the correct number of significant figures, but carry forward all the digits of your calculated answer for use in following calculations. 3.7e-4 M Submit This value is not correct. Please check your calculations and try again 80

Answer 1

Ans. Beer-Lambert’s Law, A = e C P             - equation 1,              

where,

                       A = Absorbance

                       e = molar absorptivity at specified wavelength (M^-1cm^-1)

                        P = path length (in cm)

                        C = Molar concentration of the solute

Given-

            A = 0.37

            e = 1.5 x 10³ M^-1 cm^-1

            L = 1.00 cm (assumed)

Now, putting the values in equation –

                        0.37 = (1.5 x 10³ M^-1 cm^-1) x C x 1.00 cm

                        Hence, C = 2.47 x 10^-4 M

Hence, [Salicylic acid] in CA1 = 2.5 x 10^-4 M