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Beer-Lambert Law:
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The Beer-Lambert Law relates the absorption of light to the properties of the material through which the light is traveling. It states that there is a linear relationship between the absorbance (A) of a solution and its concentration (c), path length (l), and molar absorptivity (ε).
The calculator uses the Beer-Lambert Law equation:
Where:
Explanation: The equation calculates how much light a substance absorbs at a particular wavelength per unit concentration and path length.
Details: Molar absorptivity is a fundamental molecular property that indicates how strongly a chemical species absorbs light at a given wavelength. It's crucial for quantitative analysis in spectroscopy and determining unknown concentrations.
Tips: Enter absorbance (typically between 0.1-1.0 for best accuracy), concentration in mol/L, and path length in cm (usually 1 cm for standard cuvettes). All values must be positive numbers.
Q1: What are typical values for molar absorptivity?
A: Values range from near 0 (no absorption) to over 100,000 L/mol·cm for strongly absorbing compounds. Most organic molecules have ε between 100-10,000 L/mol·cm.
Q2: Why is the path length important?
A: Longer path lengths result in more absorption. The standard is 1 cm, but other path lengths can be used if properly accounted for in calculations.
Q3: What are the limitations of Beer's Law?
A: The law assumes monochromatic light, dilute solutions, and no scattering or fluorescence. Deviations occur at high concentrations or with chemical associations.
Q4: How is absorbance measured?
A: Using a spectrophotometer, which measures the intensity of light before (I₀) and after (I) passing through a sample: A = log₁₀(I₀/I).
Q5: Can this be used for mixtures?
A: For mixtures, the total absorbance is the sum of individual absorbances, provided there are no interactions between components.