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Questions and Answers
What is the main principle behind spectrophotometric analysis?
What is the main principle behind spectrophotometric analysis?
- Absorption of electromagnetic radiation
- Attenuation of electromagnetic radiation (correct)
- Scattering of electromagnetic radiation
- Reflection of electromagnetic radiation
How is electromagnetic radiation described?
How is electromagnetic radiation described?
- By referring to its wavelength or frequency (correct)
- By its color and shape
- By its speed and direction
- By its density and pressure
What is the function of a spectrophotometer in measuring absorbance?
What is the function of a spectrophotometer in measuring absorbance?
- Generates electromagnetic power for the sample
- Measures the speed of light passing through the sample
- Separates light into its component wavelengths and selectively measures the intensity of the light (correct)
- Analyzes the color of the sample
What does transmittance measure?
What does transmittance measure?
What is the energy expression for electromagnetic radiation?
What is the energy expression for electromagnetic radiation?
Which unit is commonly used to express the attenuation of electromagnetic radiation?
Which unit is commonly used to express the attenuation of electromagnetic radiation?
According to Beer Lambert law, what is the absorbance (A) of the sample proportional to?
According to Beer Lambert law, what is the absorbance (A) of the sample proportional to?
What is used to correct the result obtained as several phenomena besides the absorbance of the analyte contribute to the final reading?
What is used to correct the result obtained as several phenomena besides the absorbance of the analyte contribute to the final reading?
What does the absorption spectrum graph plot to determine the maximum wavelength (λ max)?
What does the absorption spectrum graph plot to determine the maximum wavelength (λ max)?
What results in a linear relation when a graph of absorbance 'A' versus concentration 'C' is plotted for the standard solution?
What results in a linear relation when a graph of absorbance 'A' versus concentration 'C' is plotted for the standard solution?
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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.
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