10 Questions
What is the main principle behind spectrophotometric analysis?
Attenuation of electromagnetic radiation
How is electromagnetic radiation described?
By referring to its wavelength or frequency
What is the function of a spectrophotometer in measuring absorbance?
Separates light into its component wavelengths and selectively measures the intensity of the light
What does transmittance measure?
Ratio of the electromagnetic power existing in the sample to that incident on the sample
What is the energy expression for electromagnetic radiation?
$E=h\nu=hc/\lambda$
Which unit is commonly used to express the attenuation of electromagnetic radiation?
Absorbance (A)
According to Beer Lambert law, what is the absorbance (A) of the sample proportional to?
The molar concentration of the analyte (M)
What is used to correct the result obtained as several phenomena besides the absorbance of the analyte contribute to the final reading?
Blank
What does the absorption spectrum graph plot to determine the maximum wavelength (λ max)?
Absorbance (A) versus wavelength (λ)
What results in a linear relation when a graph of absorbance 'A' versus concentration 'C' is plotted for the standard solution?
Calibration curve or standard curve
Study Notes
Spectrophotometric Analysis
- The main principle behind spectrophotometric analysis is the measurement of the interaction between electromagnetic radiation and matter.
Electromagnetic Radiation
- Electromagnetic radiation is described by its frequency (ν), wavelength (λ), and speed (c), which are related by the equation: c = λν.
- The energy expression for electromagnetic radiation is E = hν, where h is Planck's constant.
Spectrophotometer
- A spectrophotometer measures the absorbance of a sample by detecting the amount of electromagnetic radiation absorbed or transmitted by the sample.
Transmittance and Absorbance
- Transmittance measures the fraction of incident radiation that is transmitted through the sample.
- Absorbance is a measure of the amount of radiation absorbed by the sample.
Beer-Lambert Law
- According to the Beer-Lambert law, the absorbance (A) of the sample is proportional to the concentration of the analyte (c) and the path length of the sample (l): A = εcl, where ε is the molar absorptivity.
Correction of Results
- A blank or reference solution is used to correct the result obtained, as several phenomena besides the absorbance of the analyte contribute to the final reading.
Absorption Spectrum
- The absorption spectrum graph plots absorbance versus wavelength to determine the maximum wavelength (λ max) of the sample.
Calibration Curve
- A graph of absorbance 'A' versus concentration 'C' is plotted for the standard solution, resulting in a linear relation.
Test your knowledge of spectrophotometric analysis and the absorption spectrum of cobalt (II) chloride with this quiz. Learn about the principles behind spectrophotometric analysis and how it is used to determine concentration in a solution.
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