Podcast
Questions and Answers
What is the commonest alkali halide used in infrared spectroscopy?
What is the commonest alkali halide used in infrared spectroscopy?
Potassium bromide has significant optical absorption lines in its high transmission region.
Potassium bromide has significant optical absorption lines in its high transmission region.
False
What is the purpose of grinding samples with potassium bromide in infrared spectroscopy?
What is the purpose of grinding samples with potassium bromide in infrared spectroscopy?
To analyze the samples and obtain an IR spectrum.
Infrared spectroscopy can be used to measure blood __________ content.
Infrared spectroscopy can be used to measure blood __________ content.
Signup and view all the answers
Match the application of infrared spectroscopy to its corresponding usage:
Match the application of infrared spectroscopy to its corresponding usage:
Signup and view all the answers
Which of the following methods involves creating a very thick suspension for IR analysis?
Which of the following methods involves creating a very thick suspension for IR analysis?
Signup and view all the answers
Nujol is a water-based solution used in infrared spectroscopy.
Nujol is a water-based solution used in infrared spectroscopy.
Signup and view all the answers
Which two materials are typically used as plates for infrared spectroscopy?
Which two materials are typically used as plates for infrared spectroscopy?
Signup and view all the answers
What does the partition ratio in gas chromatography represent?
What does the partition ratio in gas chromatography represent?
Signup and view all the answers
The partition ratio is unaffected by temperature and nature of the solvent.
The partition ratio is unaffected by temperature and nature of the solvent.
Signup and view all the answers
What is primarily determined by X-ray powder diffraction?
What is primarily determined by X-ray powder diffraction?
Signup and view all the answers
Name one application of gas chromatography.
Name one application of gas chromatography.
Signup and view all the answers
The three physical transport phenomena controlling gas chromatography are flow, diffusion, and __________.
The three physical transport phenomena controlling gas chromatography are flow, diffusion, and __________.
Signup and view all the answers
X-ray powder diffraction can provide information on the unit cell dimensions of crystalline materials.
X-ray powder diffraction can provide information on the unit cell dimensions of crystalline materials.
Signup and view all the answers
What is the Bragg Equation used in X-ray diffraction?
What is the Bragg Equation used in X-ray diffraction?
Signup and view all the answers
Which factor does NOT affect the partition ratio in gas chromatography?
Which factor does NOT affect the partition ratio in gas chromatography?
Signup and view all the answers
In the study of X-ray diffraction, the angle at which constructive interference occurs is referred to as the angle ___ in the Bragg Equation.
In the study of X-ray diffraction, the angle at which constructive interference occurs is referred to as the angle ___ in the Bragg Equation.
Signup and view all the answers
Match the following applications with their primary purpose:
Match the following applications with their primary purpose:
Signup and view all the answers
When dynamic equilibrium is established, the concentration of solute molecules in each phase is __________.
When dynamic equilibrium is established, the concentration of solute molecules in each phase is __________.
Signup and view all the answers
Match the following components in X-ray powder diffraction to their functions:
Match the following components in X-ray powder diffraction to their functions:
Signup and view all the answers
In X-ray powder diffraction, the sample rotates in the path of the beam at an angle of ____.
In X-ray powder diffraction, the sample rotates in the path of the beam at an angle of ____.
Signup and view all the answers
Gas chromatography only applies to analysis of solid samples.
Gas chromatography only applies to analysis of solid samples.
Signup and view all the answers
The measurement of intensity peaks in X-ray diffraction signifies destructive interference of X-rays.
The measurement of intensity peaks in X-ray diffraction signifies destructive interference of X-rays.
Signup and view all the answers
List one application of powder X-ray diffraction in scientific fields.
List one application of powder X-ray diffraction in scientific fields.
Signup and view all the answers
Which electronic transition is associated with compounds containing multiple bonds like alkenes and alkynes?
Which electronic transition is associated with compounds containing multiple bonds like alkenes and alkynes?
Signup and view all the answers
N → π* transitions absorb in the UV region above 300 nm.
N → π* transitions absorb in the UV region above 300 nm.
Signup and view all the answers
What type of compounds typically undergo n → σ* transitions?
What type of compounds typically undergo n → σ* transitions?
Signup and view all the answers
The absorption maxima for σ → σ* transitions in saturated hydrocarbons like Methane and Ethane is around _____ nm.
The absorption maxima for σ → σ* transitions in saturated hydrocarbons like Methane and Ethane is around _____ nm.
Signup and view all the answers
Match the following electronic transitions with their characteristics:
Match the following electronic transitions with their characteristics:
Signup and view all the answers
Which of the following compounds will likely undergo π → π* transitions?
Which of the following compounds will likely undergo π → π* transitions?
Signup and view all the answers
N → σ* transitions are considered forbidden and only theoretically possible.
N → σ* transitions are considered forbidden and only theoretically possible.
Signup and view all the answers
What is the typical wavelength region for the absorbance of compounds undergoing π → π* transitions?
What is the typical wavelength region for the absorbance of compounds undergoing π → π* transitions?
Signup and view all the answers
Which of the following can be identified using IR spectroscopy?
Which of the following can be identified using IR spectroscopy?
Signup and view all the answers
Raman spectroscopy can only analyze solid substances.
Raman spectroscopy can only analyze solid substances.
Signup and view all the answers
Who discovered the Raman effect?
Who discovered the Raman effect?
Signup and view all the answers
Moisture- and protein-sensitive diffuse reflectance near-infrared spectroscopy establishes the time of _____ from skeletal remains.
Moisture- and protein-sensitive diffuse reflectance near-infrared spectroscopy establishes the time of _____ from skeletal remains.
Signup and view all the answers
Match the following spectroscopic techniques with their primary applications:
Match the following spectroscopic techniques with their primary applications:
Signup and view all the answers
What happens to a person's bones at the time of death?
What happens to a person's bones at the time of death?
Signup and view all the answers
The Raman effect involves light scattering at right angles from a sample.
The Raman effect involves light scattering at right angles from a sample.
Signup and view all the answers
What principle does diffuse reflectance near-infrared spectroscopy work on?
What principle does diffuse reflectance near-infrared spectroscopy work on?
Signup and view all the answers
What are Stokes lines in a Raman spectrum?
What are Stokes lines in a Raman spectrum?
Signup and view all the answers
Anti-Stokes bands are generally more intense than Stokes bands.
Anti-Stokes bands are generally more intense than Stokes bands.
Signup and view all the answers
What causes Raman scattering?
What causes Raman scattering?
Signup and view all the answers
Anti-Stokes bands are measured with __________ samples.
Anti-Stokes bands are measured with __________ samples.
Signup and view all the answers
Match the following terms with their descriptions:
Match the following terms with their descriptions:
Signup and view all the answers
Why do Stokes lines appear in the Raman spectrum?
Why do Stokes lines appear in the Raman spectrum?
Signup and view all the answers
Fluorescence does not interfere with Stokes bands.
Fluorescence does not interfere with Stokes bands.
Signup and view all the answers
What type of molecular vibrations do intense Raman scattering occur from?
What type of molecular vibrations do intense Raman scattering occur from?
Signup and view all the answers
Study Notes
Instrumentation - Forensic Analysis
- Light travels in straight lines, but this concept can't explain phenomena like interference, refraction, and diffraction.
- Light is understood to travel in waves, explaining these phenomena.
- Light's properties can be explained by both wave and corpuscular theories.
- Radiant energy is transmitted from one body to another as radiation.
- Radiant energy associates with electric and magnetic fields, known as electromagnetic radiation.
- Electromagnetic radiation is emitted by fluctuating magnetic and electric fields.
- Examples of electromagnetic radiation include infrared, ultraviolet, X-rays, radio waves, and microwaves.
Characteristics of Electromagnetic Radiation
- Electromagnetic radiation consists of discrete energy packages called photons.
- Photons consist of oscillating electric and magnetic fields.
- The electric and magnetic fields in electromagnetic radiation are perpendicular to each other.
- Electromagnetic radiation is characterized by wavelength, frequency, or wave number.
Spectroscopy
- Spectroscopy studies the interaction of matter with light, using light emission and absorption spectra.
- Various types of spectroscopy exist, including UV-Vis, IR, X-ray diffraction, mass, atomic absorption, and NMR spectroscopy.
- UV-Vis spectroscopy measures the attenuation of light passing through a sample.
- UV-Vis spectroscopy is useful for determining the number of conjugated double bonds.
- UV spectroscopy is useful for detecting functional groups, impurities, and conjugation within various molecules.
- UV region extends from 150 nm to 800 nm.
- Visible from 400nm to 800 nm.
- Principle of Ultraviolet-Visible Spectroscopy
- Absorption of UV radiation promotes outer shell electrons to higher energy levels. -Paired (opposite) spin electrons in the ground state. -Paired (excited) spin electrons in the excited state. -Excited triplet state is stable and of lower energy than singlet state.
- UV spectroscopy is not useful below 200 nm due to nitrogen and oxygen absorbance. This is the vacuum UV region.
Infrared Spectroscopy
- Infrared (IR) spectroscopy provides structural information about a compound.
- Absorption of IR radiation causes molecular bonds to stretch and bend.
- IR radiation lies between the visible and microwave parts of the electromagnetic spectrum.
- IR spectra show vibrational transitions in molecules, acting as a vibrational fingerprint.
- IR spectra use Fourier transform to convert raw data into actual spectra. The ordinary IR region extends from 2.5 µm to 15 µm. Near IR (0.8 to 2.5 µm) and Far IR (15 to 200 µm).
- Principle of Infrared Spectroscopy
- Absorption in the IR region is due to changes in vibrational and rotational energy levels.
- Absorption of radiation with frequencies less than 100 cm-1 causes molecular rotations.
- Absorption of radiation with frequencies between 102 and 104 cm-1 causes molecular vibrations.
Finger Print Region
- Specific absorption patterns present below 1500 cm-1.
- Critically important for identification of compounds.
- These patterns are unique to each compound. The region below 1500 cm-1 is rich with bending and stretching vibrations acting as a fingerprint of a molecule.
Raman Spectroscopy
- Raman spectroscopy analyzes vibration, rotation, and low frequency modes within a system.
- This approach utilizes laser light to illuminate a sample and detect scattered light with different frequencies. Raman Spectroscopy is a versatile method that helps in the identification of molecules based on the frequency of scattered light.
- The Raman effect occurs when light interacts with a substance, causing a change in the frequency of scattered light.
Mass Spectrometry
- Mass spectrometry is an analytical technique for measuring the mass-to-charge ratio of ions.
- It's used to quantify known materials, identify unknown compounds, and determine the structure and properties of different molecules.
- It involves generating ions, separating them based on their mass-to-charge ratio, and measuring their abundances.
X-Ray Fluorescence
- X-ray fluorescence (XRF) is a non-destructive method for determining elemental composition.
- The method excites elements in a material with primary X-rays generating characteristic secondary X-rays ("fingerprints") unique to each element.
- Qualitative and quantitative analysis of material composition is therefore possible.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz focuses on the fundamental concepts of electromagnetic radiation and its implications in forensic analysis. Explore how light behaves as both a wave and a particle, as well as its significance in various applications such as infrared and X-rays.
