Chemistry [Spectrophotometry difficult example]

  • Thread starter Thread starter Dousin12
  • Start date Start date
  • Tags Tags
    Chemistry Example
Click For Summary

Discussion Overview

The discussion revolves around a homework problem related to spectrophotometry, specifically applying Lambert's Beer law to calculate absorbance in a solution containing multiple substances. Participants are exploring how to set up the equations necessary to solve the problem, given limited information.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses uncertainty about how to set up the equations for the problem, indicating a lack of information.
  • Another participant asserts that all necessary information is available and suggests that the observed absorbance can be considered as the sum of individual absorbances.
  • A participant questions the rationale behind the equation 0.183 = 9970*concentration of Fe + 34*concentration of copper, seeking clarification on why this relationship holds.
  • Further responses emphasize that the additive nature of absorbance is a key concept, suggesting that each substance contributes to the total absorbance independently.
  • Some participants express ongoing difficulty in understanding the additive property of absorbance, prompting further inquiries into this principle.

Areas of Agreement / Disagreement

Participants do not reach a consensus, as some express confusion regarding the additive nature of absorbance while others assert its validity. The discussion remains unresolved regarding the participants' understanding of the concept.

Contextual Notes

Limitations include potential misunderstandings of the additive property of absorbance and the specific conditions under which Lambert's Beer law applies. There may also be unresolved mathematical steps in the participants' attempts to set up the equations.

Who May Find This Useful

Students studying spectrophotometry, particularly those working on homework problems involving absorbance calculations in solutions with multiple components.

Dousin12
Messages
43
Reaction score
0

Homework Statement


349fce81d2206bdcd2d1a6293b2e70bc.png


Homework Equations


A=epsilon*l*c

The Attempt at a Solution


So I was wondering on how to set up the equations now, since I don't have much information? Which equations should i use to solve the problem?
 
Physics news on Phys.org
You have all the information needed. Assume the observed absorbance is the sum of individual absorbances.
 
Please help me understand how I should set up the equations!

91ebaf011f2f50623d16ab8bc7d8c5e0.png


This is a big questionmark to me, why u should this?
0.183 = 9970*concentration of Fe + 34*concentration of cupper. Why is 0.183 equal to that?
 
This is a direct application of the Lambert's Beer law which you wrote in your first post, and the fact that the observed absorbance is a sum of absorbances of copper and iron.

Assuming there is no copper, can you write formulas for the absorbances of the solution at both wavelengths? Can you do the same for iron? Can you add these values?
 
I still have really difficult! To understand why you add these values!
 
Dousin12 said:
I still have really difficult! To understand why you add these values!

Which part of the "absorbance is additive" statement is not clear to you?

If there is more than one substance present in the solution, each absorbs on its own, so the observed total absorbance is a sum of individual absorbances (at least for relatively diluted solutions).
 

Similar threads

  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 13 ·
Replies
13
Views
4K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 5 ·
Replies
5
Views
4K
  • · Replies 2 ·
Replies
2
Views
2K