Home
Back
Molarity From Absorbance Formula:
| From: | To: |
The Molarity From Absorbance formula is derived from the Beer-Lambert law, which relates the absorption of light to the properties of the material through which the light is traveling. It allows calculation of concentration from measured absorbance values.
The calculator uses the Beer-Lambert law formula:
Where:
Explanation: The formula calculates the concentration of a solution based on how much light it absorbs, the substance's inherent ability to absorb light, and the distance the light travels through the solution.
Details: Accurate molarity calculation is essential in analytical chemistry, biochemistry, and pharmaceutical sciences for determining solution concentrations, conducting quantitative analysis, and preparing standard solutions.
Tips: Enter absorbance (unitless), molar absorptivity in M⁻¹ cm⁻¹, and path length in cm. All values must be valid (absorbance ≥ 0, molar absorptivity > 0, path length > 0).
Q1: What is the Beer-Lambert law?
A: The Beer-Lambert law states that the absorbance of light by a solution is directly proportional to the concentration of the absorbing species and the path length of the light through the solution.
Q2: What are typical values for molar absorptivity?
A: Molar absorptivity values range from near 0 to over 100,000 M⁻¹ cm⁻¹, depending on the substance and wavelength of light used.
Q3: What is the standard path length for cuvettes?
A: Most standard cuvettes have a path length of 1.0 cm, though other sizes (0.1 cm, 1.5 cm, etc.) are also available.
Q4: Are there limitations to this formula?
A: The Beer-Lambert law assumes monochromatic light, dilute solutions, and that absorbance is solely due to the analyte of interest without interactions between molecules.
Q5: What is the valid absorbance range for accurate measurements?
A: For most accurate results, absorbance values should be between 0.1 and 1.0 absorbance units, as values outside this range may suffer from significant measurement errors.