To determine the relationship between absorbance versus concentration of crystal

Question

To determine the relationship between absorbance versus concentration of crystal violet, a Beer’s law calibration curve of absorbance versus concentration of crystal violet, [CV+], was prepared in the pre-lab exercise for investigation 9. Linear regression analysis of the calibration curve data yielded the equation: Absorbance = 48983 x M + 0.00148. During the investigation, the absorbance of a crystal violet solution in the presence of hydroxide ions was monitored at 565 nm until a value of 0.200 was reached. The next step in the investigation was to convert the linear range absorbance values into concentrations using the Beer’s law calibration curve equation. Show how you would calculate the concentration of the crystal violet solution corresponding to an absorbance of 0.548.

Explanation / Answer

we have the equation of straight line by drawing a plot between Concentration( x axis) vs absorbance. Equation is

Absorbance = 48983 x M + 0.00148

or y = 48983 x M + 0.00148

here y is the absorbance

and 48983 is the slop of the line

M is the x value or concentration value

0.00148 is the intercept.

Now, Calculate the concentration corresponding to absorbance of 0.200

that is 0.200 = 48983 x M + 0.00148

48983 M = 0.200- 0.00148

M = ( 0.19852 ) / 48983

= 0.000004053 Molar

2.

Calculate the concentration when the absorbance = 0.548

substitute in the above equation,

0.548 = 48983 x M + 0.00148

48983 M = 0.548- 0.00148

M =(0.54652 ) / 48983 =0.000011157 Molar

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