Spectrophotometry and Beer-Lamberts Law

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In summary, a molecule with a spectral line at 27319 cm-1 has a wavelength of 0.0367 cm and a frequency of 8.62 x 10^9 Hz. The equation A=εCl can be used to calculate the absorbance of the molecule, where A is the absorbance, ε is the molar extinction coefficient, C is the concentration, and l is the path length. However, the concept of frequency being equal to 1/wavelength is incorrect, as these two quantities have different units.
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joeyjo100
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Homework Statement


A molecule has a spectral line at 27319 cm-1

what is its wavelength?
what is its frequency?


Homework Equations


A=εCl
where A=absorbance, ε=molar extinction coefficient, C=concentration and l=path length

The Attempt at a Solution


thought about doing 1 over the spectral line for the wavelength, and correcting the units, but then realized frequency is 1 over the wavelength, which would just be the original answer

If I'm honest, i am not sure what it means by a spectral line, think the question may be badly worded
 
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Frequency is not 1/wavelength. It's easy to see that this equation is not true by looking at the units. Frequency has units of inverse time (e.g. s-1). Wavelength has units of distance (e.g. m). 1/wavelenght does not give units of inverse time.

Frequency is (speed of the wave)/wavelength. You can check the units to see that dividing a speed by a distance give units of inverse time.
 

FAQ: Spectrophotometry and Beer-Lamberts Law

What is spectrophotometry and how does it work?

Spectrophotometry is a technique used to measure the amount of light absorbed or transmitted by a substance. It works by passing a beam of light through a sample and measuring the amount of light that is absorbed at different wavelengths. This information can then be used to determine the concentration of a substance in the sample.

What is Beer-Lambert's Law and how is it related to spectrophotometry?

Beer-Lambert's Law is a mathematical relationship that describes the relationship between the concentration of a substance in a sample and the amount of light absorbed by that sample. It states that the amount of light absorbed is directly proportional to the concentration of the substance and the distance the light travels through the sample.

What are the main applications of spectrophotometry?

Spectrophotometry has a wide range of applications in various fields such as chemistry, biochemistry, environmental science, and pharmaceuticals. It is commonly used to determine the concentration of a substance in a sample, identify unknown substances, and monitor chemical reactions.

What are the advantages of using spectrophotometry?

Some of the key advantages of spectrophotometry include its high sensitivity, accuracy, and precision. It also allows for rapid and non-destructive analysis of samples, making it a valuable tool in research and quality control processes. Additionally, spectrophotometry can be used for both qualitative and quantitative analysis, making it a versatile technique.

Are there any limitations to using spectrophotometry?

While spectrophotometry is a powerful analytical technique, it does have some limitations. It is only applicable to substances that absorb light in the visible or ultraviolet regions of the electromagnetic spectrum. Additionally, the sample must be in a liquid or transparent form, which may limit its use in certain applications. Furthermore, the accuracy of spectrophotometric measurements can be affected by factors such as sample impurities and instrument calibration.

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