Plot the following data points and determine the equation

Question

Using a spreadsheet software, plot the following data points and determine the equation for the line of the calibration curve.

Concentration (M)	Absorbance
1	0.9882
0.1	0.1439
0.01	0.0526
0.001	0.0361
0.0001	0.0223

Answer 1

Hello, Ely,

When I plot the data points, I see what appears to be a rapid increase of absorbance with increasing concentration that becomes more like a linear relationship at around 0.01M. To understand this, I calculated the slope of the line at difference locations, between each of the data points.

As you can see, the slope rises quickly at low concentration, then becomes more linear, having a function of y = 1x + b. We don't have enough information to calculate b, but it should be close to zero if the instrument is calibrated and nulled with a stock solution containing none of the absorbing species being measured.

The difficultly comes in finding an equation that also handles the rapid early rise in absorbance. .

Bob