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Beer's Law:
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Molar absorptivity (ε), also known as the molar extinction coefficient, is a measurement of how strongly a chemical species absorbs light at a given wavelength. It is a fundamental property in spectrophotometry and is used in Beer's Law to quantify the concentration of substances in solution.
The calculator uses Beer's Law:
Where:
Explanation: Beer's Law states that absorbance is directly proportional to the concentration of the absorbing species and the path length through which light travels.
Details: Molar absorptivity is crucial for quantitative analysis in chemistry and biochemistry. It allows researchers to determine unknown concentrations of substances, identify compounds, and study chemical reactions through spectrophotometric methods.
Tips: Enter absorbance (unitless), concentration in mol/L, and path length in cm. All values must be positive numbers. The calculator will compute the molar absorptivity in L/mol·cm.
Q1: What is the typical range for molar absorptivity values?
A: Molar absorptivity values typically range from 0 to over 100,000 L/mol·cm, with higher values indicating stronger light absorption.
Q2: Does molar absorptivity depend on wavelength?
A: Yes, molar absorptivity is wavelength-dependent. Each compound has a characteristic absorption spectrum with maximum absorption at specific wavelengths.
Q3: What are the limitations of Beer's Law?
A: Beer's Law assumes monochromatic light, dilute solutions, and no chemical interactions. Deviations can occur at high concentrations or with complex chemical systems.
Q4: How is molar absorptivity determined experimentally?
A: It is typically determined by measuring absorbance at known concentrations and path length, then calculating ε from the slope of the absorbance vs. concentration plot.
Q5: What units are used for molar absorptivity?
A: The standard units are L/mol·cm, though sometimes M⁻¹cm⁻¹ is used, which is equivalent.