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Molar Absorptivity Equation:
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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 constant in Beer's law that relates the absorption of light to the properties of the material through which the light is traveling.
The calculator uses Beer's law equation:
Where:
Explanation: This equation calculates how much light a substance absorbs per mole per centimeter of path length at a specific wavelength.
Details: Molar absorptivity is crucial in quantitative spectroscopy for determining concentrations of unknown solutions, identifying substances, and understanding molecular structure and electronic transitions.
Tips: Enter absorbance (typically between 0.1-1.0 for accurate measurements), concentration in mol/L, and path length in cm. All values must be positive and concentration and path length must be greater than zero.
Q1: What is a typical range for molar absorptivity values?
A: Values typically range from 0 to over 100,000 L/mol·cm, with higher values indicating stronger absorption.
Q2: Does molar absorptivity depend on wavelength?
A: Yes, molar absorptivity is wavelength-dependent and is usually reported at the wavelength of maximum absorption (λmax).
Q3: What are the limitations of Beer's law?
A: Beer's law assumes monochromatic light, dilute solutions, and no chemical associations or dissociations. It may deviate at high concentrations.
Q4: How is molar absorptivity used in practice?
A: It's used to create calibration curves for quantitative analysis, determine unknown concentrations, and characterize chemical compounds.
Q5: Can molar absorptivity be negative?
A: No, molar absorptivity is always positive since it represents the ability of a substance to absorb light.