1. What is Molar Absorption Coefficient?

The molar absorption coefficient (ε), also known as molar absorptivity or extinction coefficient, is a measure of how strongly a chemical species absorbs light at a given wavelength. It is a fundamental parameter in spectroscopy and quantitative analysis.

2. How Does the Calculator Work?

The calculator uses the Beer-Lambert law:

Where:

• \( \varepsilon \) — Molar absorptivity (L/mol·cm)
• \( A \) — Absorbance (unitless)
• \( c \) — Concentration (mol/L)
• \( l \) — Path length (cm)

Explanation: The Beer-Lambert law describes the linear relationship between absorbance and concentration of an absorbing species.

3. Importance of Molar Absorptivity

Details: Molar absorptivity is crucial for quantitative analysis in spectroscopy, determining unknown concentrations, characterizing compounds, and validating analytical methods in chemistry and biochemistry.

4. Using the Calculator

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 numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical range for molar absorptivity values?
A: Values range from near 0 for weak absorbers to over 100,000 L/mol·cm for strong chromophores. Values above 10,000 are considered strong absorbers.

Q2: Does molar absorptivity depend on wavelength?
A: Yes, ε is wavelength-dependent and is typically reported at the wavelength of maximum absorption (λmax).

Q3: What factors affect molar absorptivity?
A: Molecular structure, solvent, temperature, pH, and wavelength all influence the value of ε.

Q4: How is this different from specific absorptivity?
A: Specific absorptivity uses concentration in g/L rather than mol/L, making it useful when molecular weight is unknown.

Q5: What are the limitations of the Beer-Lambert law?
A: The law assumes monochromatic light, non-interacting molecules, and concentrations where absorbance is linear (typically A < 1.0).