To determine the exact concentration of a solution, it is best to use Beer\'s La

Question

To determine the exact concentration of a solution, it is best to use Beer's Law, which relates mathematically the concentration of a solution to the colour intensity: where: A = absorbance (a numerical value related to the intensity of the colour) e = the molar absorptivity of the coloured species (a constant value for a given compound and wavelength of light) I = the length the light travels through solution during the measurement. The product of the constants e & l can be determined by measuring the absorbance of solutions of known concentration using a spectrophotometer. A graph (like the one shown below) can then be prepared - it is known as a "calibration curve". Using the graph provided below, determine the value of (el) for Compound Z.

Explanation / Answer

slope of the above graph (m) = (y2-y1)/(x2-x1)

Here (x1,y1) = (0,0) and (x2,y2) = (0.0003,1.4)

Therfore, slope = 1.4/0.0003 = 4666.6667

the graph is of form y = mx where y = absorbance , x = concentration which implies m =El =4666.6667

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