Concentrations In my experiment I obtained a calibration curve of y= 2539x+ 0.08

Question

Concentrations

In my experiment I obtained a calibration curve of y= 2539x+ 0.0875. Find the molar absorption coefficient for [CrO4 2-] and the error for molar absorption coefficient when the path length = 1.38 cm.

I believe the molar absorption coefficient is 2539, but I am unsure of how to find the Error for molar absorbtion coefficient?

From the calibration curve we are supposed to determine the solubility -product constant of Ag2CrO4. we have a path length of 1.21 cm and absorbancies of .490, .498, and .358

I know in order to do this we need to find the Molar concentration of [CrO4], would we use the molar absorption coefficient from the calibration curve or the error for molar absorption coefficient to find this?

2.4x10^-5 .071 1.2x10^-4 .460 2.4x10^-4 .778 3.6x10^-4 .930

Explanation / Answer

1) we know that

molar absorptivity = absorbance/(path length of cuvette x concentration)
a) molar absorptivity = 0.071 / 1.38 X 2.4 X 10^-5 = 2143.71

b) molar absorptivity = 0.46 / 1.2 X 10^-4 X 1.38 = 2777.77

c) molar absorptivity = = 0.778 / 2.4 X 10^-4 X 1.38 = 2349.08

d) moalr absrobptitivity = 0.93 / 1.38 x 0.36 X 10^-4 = 1972.62

Lets take average = 2310.79

Now substract all values from the average take their squares and add and take average

That will give standard deviation = 300.75

so the error will be 300.75

2) We will use the value from graph only not the error or uncertainity

value average substracted squared 2143.71 2310.79 167.08 27915.73 2777.77 2310.79 -466.98 218070.3 2349.08 2310.79 -38.29 1466.124 1972.62 2310.79 338.17 114358.9

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