Sciencemadness Discussion Board

Trouble with excel graph, need help!

GreenD - 13-2-2012 at 13:53

That value for your slope is not epsilon, I don't know why you think that.

Beer's law is A=ebc
e = epsilon [Liters / (mol • cm)]
b = path length
c = concentration

Your slope is Absorbance / concentration.
You still need b to calculate epsilon.

e= Abosrbance / (Concentration * cm)
What is the path length?

[Edited on 13-2-2012 by GreenD]

[Edited on 13-2-2012 by GreenD]

GreenD - 13-2-2012 at 14:05

I just did the plot myself and got a slop of 3.1

not sure what you did there.

GreenD - 13-2-2012 at 14:18

I figured it out. Look at the spacings on your x-axis.
they go; 4, 8, 12, etc - not sure how you accomplished that, but your slope is logarithmic or exponential. . .

White Yeti - 13-2-2012 at 14:44

Quote: Originally posted by GreenD  
That value for your slope is not epsilon, I don't know why you think that.

Beer's law is A=ebc
e = epsilon [Liters / (mol • cm)]
b = path length
c = concentration

Your slope is Absorbance / concentration.
You still need b to calculate epsilon.

e= Abosrbance / (Concentration * cm)
What is the path length?


I know, but since the path length remains constant throughout the whole experiment, its value is trivial. I will find epsilon by dividing the slope of the graph by the path length, but to find the concentration, I will have to multiply epsilon by the path length, leading back to where I started.

I will check my x axis markings once again and will reply the problem is solved.

White Yeti - 13-2-2012 at 15:25

Problem solved. I chose the wrong scatterplot option -.-
Thanks for the help. I'll delete the useless thread now.