Beer Lambert Law: Solving Qs for Pharmacy Students

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Discussion Overview

The discussion revolves around the Beer-Lambert Law, specifically focusing on solving related questions for pharmacy students. The scope includes theoretical understanding and practical application of the law in the context of pharmaceutical calculations.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant seeks help with specific questions related to the Beer-Lambert Law, including definitions and calculations involving absorbance, concentration, and dissolution tests.
  • Another participant provides the formula for the Beer-Lambert Law, A = εlc, and identifies the variables involved.
  • There is a request for clarification on which values to use in the equation, indicating some uncertainty about the application of the law.
  • A participant expresses frustration at the lack of understanding and admits to confusion over the calculations, suggesting they may have missed steps in the process.
  • One participant suggests using Google for additional resources, indicating a reliance on external materials for clarification.
  • Another participant asks for specifics on what values are being used for different parts of the problem, highlighting the need for detailed input in the calculations.

Areas of Agreement / Disagreement

Participants generally agree on the use of the Beer-Lambert Law and its formula, but there is no consensus on the specific calculations or the approach to solving the questions posed. Multiple views on how to proceed with the calculations remain evident.

Contextual Notes

Some participants express uncertainty about the steps involved in the calculations and the definitions of terms, indicating potential gaps in their understanding of the material. There are also references to missing explanations in textbooks and lecture notes.

Who May Find This Useful

Pharmacy students or individuals studying the Beer-Lambert Law and its applications in pharmaceutical contexts may find this discussion relevant.

UKstudent
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Hi, I'm an pharmacy student and I've forgotten how to answer questions on the beer lambert law. I would be grateful if anyone could show me how to answer these questions below.

(a)In pharmaceutics it is usual to use the specific absorption coefficient A (1%, 1 cm). What is this term?
(2 marks)

(b)The A(1%, 1cm) value for paracetamol in 0.1M sodium hydroxide is 715 at a wavelength of 257 nm. Calculate the concentration in μg/ml of a solution of paracetamol in 0.1M sodium hydroxide which gives an absorbance of 0.9 in a cell of pathlength 1 mm.
(6 marks)

(c)The concentration calculated in part (b) was as a result of a sample taken at 45 minutes from a dissolution test of a conventional release 500 mg paracetamol tablet. The volume of the dissolution medium was 900 ml. Calculate the amount of paracetamol (in mg) dissolved in the vessel and the percentage released from the 500 mg paracetamol tablet.
(4 marks)


Many thanks!
 
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Beer-Lambert's law, if I remember correctly, is A=\epsilonlc, where A is absorbance, \epsilon is absorption cross-section, l is path length, and c is concentration.
 
Yep, you're correct. Any ideas on which numbers to plug in into that equation?
 
Those given in the questions.
 
LOL. so tell me then, what would be my A, L,E and concentration values.
 
Have you actually read the question, or are you just hoping someone will do it for you? Some parameters are given explicit values and are called identical in both your post and kldickson's post. Other may require a little bit of tinkering, but they are all there.

--
 
See that’s the thing. I’ve forgotten completely how to answer questions like this. My book doesn’t explain it and neither is it in the lecture notes. So I would plug these values into the equ:
A= lc

0.9=0.1c

so 9=c….at which point I doubt my answer.

Moles=mass/conc

So 0.1= 151/c
So c=1510
And at this point I know I’ve missed out a step or am making stuff up. Just really confused.
 
What are you plugging in for equations B and C?
 

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