1
$\begingroup$

What is the molar absorptivity of copper sulfate? I am trying to find the molarity of copper sulfate solution by absorption in a spectrophotometer with a cuvette.

However, I can't find $\varepsilon$, the molar absorptivity coefficient of $\ce{CuSO4}$. I searched it up online, and I found experimental data saying that is $\pu{2.81 L mol-1 cm-1}$, but another source says that it is $0.91$.

I have searched on various databases including NIST's, but I couldn't find anything. Is there a definite molar absorptivity for everything, or is it all experimental?

$\endgroup$
  • 1
    $\begingroup$ The value will depend on wavelength so both the values above could be correct; it would be worth checking. Also if you can, measure absorbance vs. concentration. The eqn. is $A=\epsilon [C]l$ where l is the cell path length and $\epsilon $ the extinction coefficient in $\pu{dm^2mol^{-1}cm^{-1}}$ $\endgroup$ – porphyrin May 13 '17 at 12:11
  • $\begingroup$ Right, I searched up 635nm, but I forgot to make sure that it was actually that. Thanks for reminding me $\endgroup$ – abcdefg May 13 '17 at 20:08
0
$\begingroup$

The molar absorptivity of copper sulfate in water at 810 nm (the position of the absorbance maximum) is about 12.3 L/mol/cm

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.