A calibration curve for the orange dye in a soft drink was o

A calibration curve for the orange dye in a soft drink was obtained by plotting absorbance against concentration (M) for a series of solutions of known concentration. The slope of the calibration curve was 226 L/mol and the intercept was -0.011. The absorbance of an unknown soft drink was found to be 0.333 under the same conditions as the calibration curve. Calculate the concentration of the orange dye in the soft drink.

Solution

Ans:

Beer\'s law should be used to calculate the concentration.

The equation for Beer\'s law is: A = mCl

(A=absorbance, m = molar extinction coefficient, C = concentration, l=path length of 1 cm)

You should have a data set which was used to create a standard curve. The graph should plot concentration (independent variable) on the x-axis and absorption (dependent variable) on the y axis.

You\'ll need to add a line of best fit to the data points and determine the equation for the line. The equation should be in y=mx + b

y = absorbance (A)
Note: no unit for absorbance

x = concentration (C)
Note: unit is M or mol/L

m = (m) = slope or the molar extinction coefficient in beers law which has units of#M^-1cm^-1#

So A = mC +b

If you solve for C you should get
C = (A-b)/m

So if you substract your y-intercept from the absorbance and divide by the slope, you are finding the concentration of your sample.