A series of six solutions was prepared at the given concentrations. Sample A B C D E F Concentration (mM) 50 100 150 200 300 400 Set of six cuvettes. The first is pale green, and the color becomes deeper green with each successive cuvette. The absorbance of each solution was then measured using a colorimeter. Sample A B C D E F Absorbance 0.25 0.50 0.75 1.00 1.50 2.00 What is the concentration of the solution with an absorbance of 1.50

In order to solve this problem we need to calculate the line of best fit for those experimental values. The absorbance values go in the Y-axis while the concentration goes in the X-axis. We can calculate the linear fit using Microsoft Excel using the LINEST function (alternatively you can write the Y data in one column and X data in another one, then use that data to create a dispersion graph and finally add the line of best fit and its formula).

The formula for the line of best fit for this set of data is:

y = 0.005 * x

So now we calculate the value of x when y is 1.50:

1.50 = 0.005 * x

x = 300 mM