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Author Topic: Spectrophotometric Titration curve  (Read 6053 times)

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1stplace

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Spectrophotometric Titration curve
« on: April 19, 2008, 06:44:08 AM »



This is the graph and the previous part to the question that I don't get.

The question is : The spectrophotometer that was used for the titration cannot properly measure differences in light intensity by less than 1%. Using the above data, calculate the minimal concentration of the complex that can be accurately measured.

I really don't know where to start. Can somebody help me?
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Arkcon

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Re: Spectrophotometric Titration curve
« Reply #1 on: April 19, 2008, 07:04:34 AM »

So the chart should have error bars of 1%.  Given that, and the shape of the graph, what do you think of the chart?  What range is useful?  What do you think of the shape of the graph?
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ARGOS++

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Re: Spectrophotometric Titration curve
« Reply #2 on: April 20, 2008, 11:45:21 AM »

Dear Arkcon;

I don’t believe that the “Error-Bars” will be very helpful, because:
  .. differences in light intensity by less than 1%.
  -  is not very linear to Absorptions, but Absorptions is “very” linear to Concentrations!
That means that the “’1.0 %’ -Error-Bars” will have a different size over de whole Absorptions scale.

Dear 1stPlace;

As the second Question asks:
Using the above data, calculate the minimal concentration  . 
    -   it is required to solve prior the first Question, otherwise you will not have any Concentration result!

To solve the 1. Question you best “see” the Spectrometer as only a little special Indicator!
  • -   So, at how much mL’s your “Indicator” has changed its color?
  • -   And the remaining you can handle as a normal  “…….”-Titration: It’s Stoichiometry!

Then to solve the 2. Question you need the Mrs. “Beer and Lambert”, because you will have to translate:
  • -   Your Concentration and corresp. Absorption you have read from the Graph into an of εtotal!
  • -   1.0% Transmittance into its corresponding Absorption (A1.0%).
  • -   Finally you can translate your A1.0% with the help of εtotal into a Concentration.

Mrs. “Beer and Lambert” with Graphs, Formulas, and Explanations you can find on:

I hope this gives you enough help to start your both Solutions.

Good Luck!
                    ARGOS++

P.S.:  For Stoichiometry the following page may be of some help:   "Stoichiometry Problem
.
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