Introduction to Spectrophotometry

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What does the Lambert-Beer law state about absorbance?

Absorbance is directly proportional to both sample path length and concentration. (correct)

Absorbance remains constant regardless of changes in concentration.

Absorbance is independent of sample concentration.

Absorbance is inversely proportional to sample path length.

Which type of spectrophotometer measures absorbance in the range of 200 nm to 700 nm?

UV-Vis Spectrophotometer (correct)

Infrared Spectrophotometer

Fluorescence Spectrophotometer

NMR Spectrophotometer

What is the role of filters in colorimeters?

To increase the amount of light transmitted regardless of concentration.

To allow the maximal absorption wavelengths to pass and improve sensitivity. (correct)

To absorb all wavelengths of light uniformly.

To completely block the targeted wavelengths from entering the solution.

Which of the following is NOT an application of spectrophotometers?

Determining temperature of substances Signup and view all the answers

In what way does the use of cuvettes affect spectrophotometric measurements?

They allow for the passage of light through the sample without interference. Signup and view all the answers

What is one of the main differences between UV-Vis and IR spectrophotometers?

UV-Vis measures in the UV and visible range, while IR measures in the infrared range. Signup and view all the answers

Which statement correctly describes the application of spectrophotometry in hospitals?

It assists in respiratory gas analysis. Signup and view all the answers

What does the term 'structure elucidation of organic compounds' refer to in the context of spectrophotometry?

Clarifying the structural formula and arrangement of atoms in the compounds. Signup and view all the answers

What is the primary function of spectrophotometry?

To quantitatively measure light absorption and transmission by a solution. Signup and view all the answers

Why does chlorophyll make plants appear green?

It only absorbs red light and reflects green light. Signup and view all the answers

What does an absorption spectrum represent?

The amount of light absorbed at different wavelengths by a substance. Signup and view all the answers

What is a standard curve used for in spectrophotometry?

To indicate the amount of light absorbed by known concentrations for determining unknown concentrations. Signup and view all the answers

What does the Lambert-Beer Law describe?

The relationship between light absorption and the concentration of a substance. Signup and view all the answers

Which property of substances can affect how much light they absorb, despite having similar wavelengths?

Intrinsic variation in molecular structure. Signup and view all the answers

What is colorimetry an alternative term for?

The quantitative measurement of light absorption in colored solutions. Signup and view all the answers

In what scenario would one ideally use a standard curve?

To interpolate the concentration of an unknown based on its absorbance. Signup and view all the answers

Study Notes

Introduction to Spectrophotometry

Substances absorb specific light wavelengths due to their molecular structure. Chlorophyll, for example, absorbs red light but transmits green, resulting in its green appearance.
While two substances may absorb the same wavelengths, the degree of absorption differs due to variations in molecular structure.
Spectrophotometry quantitatively measures a solution's light absorption and transmission. If the solution is colored, it's called colorimetry.

Absorption Spectrum

An absorption spectrum is a graph showing a substance's light absorbance at different wavelengths. Riboflavin's absorption spectrum is given as an example (Figure 23 – not shown here).

Standard Curve

A standard curve graphs light absorption against known concentrations of a substance. It helps determine unknown concentrations by interpolating absorbance values. The Lambert-Beer Law offers a more precise method for concentration determination.

Lambert-Beer Law

The Lambert-Beer Law describes the direct proportionality between absorbance and the sample's path length and concentration.
It has broad applications in various fields, including medicine and organic chemistry.

Spectrophotometer

A spectrophotometer measures light absorption or transmission in a solution.
Some colorimeters use filters instead of monochromators and selectors to maximize sensitivity by focusing on wavelengths maximally absorbed by the solution.
Spectrophotometers are categorized by light source wavelength.
- UV-Vis spectrophotometers measure absorbance in the ultraviolet (200-700 nm) and visible range.
- IR spectrophotometers utilize infrared light (700-15000 nm).

Spectrophotometer Applications

Determining substance concentrations
Detecting impurities
Elucidating the structure of organic compounds
Monitoring dissolved oxygen in aquatic ecosystems
Characterizing proteins
Identifying functional groups
Analyzing respiratory gases in hospitals
Determining molecular weight of compounds
Identifying compound classes in pure and biological samples.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the fundamentals of spectrophotometry, including the principles of light absorption and colorimetry. Learn about the absorption spectrum and how to utilize standard curves and the Lambert-Beer Law for determining concentrations. This quiz will enhance your understanding of how substances interact with light and its applications in quantitative analysis.