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Beer-Lambert Law:
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Molar absorptivity (ε), also known as the molar extinction coefficient, is a measure of how strongly a chemical species absorbs light at a given wavelength. It is a fundamental property in spectroscopy and quantitative analysis.
The calculator uses the Beer-Lambert Law:
Where:
Explanation: The Beer-Lambert Law describes the linear relationship between absorbance and concentration of an absorbing species.
Details: Molar absorptivity is crucial for quantitative analysis in spectroscopy, determining unknown concentrations, characterizing compounds, and validating analytical methods in chemistry and biochemistry.
Tips: Enter absorbance (typically between 0.1-1.0 for best accuracy), concentration in mol/L, and path length in cm. All values must be positive numbers.
Q1: What is the typical range for molar absorptivity?
A: Values range from near 0 for weak absorbers to over 100,000 L·mol⁻¹·cm⁻¹ for strong chromophores. Most organic compounds fall between 1,000-50,000 L·mol⁻¹·cm⁻¹.
Q2: Why is path length important?
A: Path length affects the amount of light absorbed. Standard cuvettes are 1 cm, but other sizes can be used with appropriate calculations.
Q3: What affects molar absorptivity values?
A: Wavelength, solvent, temperature, pH, and molecular structure all influence ε values. It is specific to each compound under defined conditions.
Q4: Can this calculator be used for any wavelength?
A: Yes, but note that ε varies with wavelength. The calculated value applies only to the specific wavelength where absorbance was measured.
Q5: What are common applications?
A: Quantitative analysis, purity assessment, kinetic studies, equilibrium constant determination, and method validation in analytical chemistry.