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Q: Beer's law help?

JakeThe molar extinction coefficient of reduced NADH (nicotinamide adenine dinucleotide phosphophate) at 340nm is 6220 L/mole·cm. 11ml of solution containing 0.8 micromoles of NADH were placed in a cuvette of 1.6cm light path. Calculate the percentage light transmission of this sample at 340nm. Oka...

inorganic-chemistry absorption
MaxW
MaxW
This is a home work question. Please show some work. HINT - Use Beer–Lambert law.
Jake
Jake
okay so this is an equation used: Abs=ecx and i believe i have all the numbers i needed to plug it in so i did Abs=(6220L/mole.cm)(1.5cm)(0.8mM) and then find abs right? is this all i need? because "e" is suppose to be molar extinction coefficient in (L/moles.cm) "x" is 1.6cm and "c" is suppose to be the concentration of macromolecule in m/L. but i am not sure what to do with 11 ml, or do i even bother with it? any help would be much appreciated
MaxW
MaxW
You have to assume that 11 ml would be enough to fill the cuvette. Seems like more than enough. 1.6x1.6 cm cross section and 4 cm tall . // LOL - Spell check wants to use its magic to change cuvette to corvette. Gosh it should be that easy...
Not quite. What are you supposed to be calculating?
Jake
Jake
Calculate the percentage light transmission of this sample at 340nm
MaxW
MaxW
And what does you equation calculate?
Jake
Jake
18:43
well yes because i need to find Abs which is the light transmission
or is that the absorbance? but either way if it is the absorbance couldn't i subtract whatever i get from abs to get the transmission using log(1/abs)
MaxW
MaxW
The point is that you calculate the %T from the Abs. The two things are not one and the same.
Jake
Jake
i could really use some help, i did like millions of beers law practice and i am stuck on two questions and this is one of them
MaxW
MaxW
$T = 10^{-A}$ is equation to convert, 100T = %T
Jake
Jake
yes but is to get Abs right? like on my set up on my first comment based on the question?
MaxW
MaxW
EDit equion by adding a section "WORK" show your calculations...// Or add anaswer showing work...
Jake
Jake
18:43
Abs=(6220L/mole.cm)(1.5cm)(0.8mM)=7464?
then when used T=10^-A that gave me a huge number
MaxW
MaxW
What is a mM? ........
Jake
Jake
so what do i do?
it is in millimeter
Mockingbird
Mockingbird
Welcome chem.SE. Please note that it's not any homework helping site. And questions like this one will surely attract any attention because it's an conceptual misunderstanding of yours. Please, be careful.
porphyrin
porphyrin
In your equation 'Abs' is usually called optical density and is what a spectrophotometer conventionally plots vs wavelength in an absorption spectrum. You need to convert the amount of NADH into concentration; I'm not sure if by $0.8$ micromoles you mean a concentration or just this amount in $11$ ml.
MaxW
MaxW
Well it should be $\mu\text{M}$ or micromoles
Martin - マーチン
Martin - マーチン
18:43
Welcome to Chemistry.SE! Take the tour to get familiar with this site. Mathematical expressions and equations can be formatted using $\LaTeX$ syntax. Comments are not for extensive conversation. Please edit your question to include your efforts so that it can be reopened and answered.
I have merged your questions, and reopened since the duplicate target is gone. Try to use the information in the comment above to restyle your question. Give it a better, actually meaningful title. Add more context and your thought process.

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