All Flashcards
Label the components of a basic spectrophotometer.
1: Light Source, 2: Monochromator, 3: Sample, 4: Detector, 5: Readout
Label the parts of the monochromator.
1: Entrance Slit, 2: Dispersion Device, 3: Exit Slit
Define Spectrophotometry.
Technique for measuring a substance's light absorption to determine its concentration.
What is a monochromator?
Part of a spectrophotometer that selects a specific wavelength of light.
Define absorbance (A).
The measure of a substance's capacity to absorb light of a specified wavelength.
What is molar absorptivity ()?
A measure of how strongly a chemical species absorbs light at a given wavelength (L/mol·cm).
Define path length (b).
The distance the light travels through the sample, usually the width of the cuvette (cm).
Define complementary colors.
Colors opposite each other on the color wheel; a substance absorbs its complementary color most strongly.
What are the steps to using a spectrophotometer?
- Prepare sample in cuvette. 2. Select appropriate wavelength using the monochromator. 3. Place cuvette in spectrophotometer. 4. Measure absorbance or transmittance. 5. Use Beer-Lambert Law to determine concentration.
How do you determine concentration using the Beer-Lambert Law?
- Measure absorbance (A) of the solution. 2. Know the molar absorptivity () and path length (b). 3. Use the formula A = bc to solve for concentration (c).