Extra for chapter 5&6

Question 1

How does infrared spectroscopy work

Answer 1

• Excites the molecules of a compound and produces an infrared spectrum of the energy absorbed by a molecule as a function of the frequency or wavelength of light
• Different types of bonds react differently to IR radiation
• Triple and double bonds, for example, are shorter and stiffer than single bonds and thus vibrate at higher frequencies
• The types of atoms in the bonds are also important. Because O-H bonds are stronger
  than C-H bonds, they vibrate at higher frequencies
• As a result, IR spectroscopy allows us to identify the various functional groups
  present in a compound

Question 2

What is the necessary condition for IR spectroscopy

Answer 2

According to the selection rule for IR transitions, the change in the electric dipole moment of the functional group present in a
molecule or sample during the vibration is required for a molecule or sample to show an infrared spectrum

Question 3

How does the IR spectroscopy instrument work

Answer 3

• First, an IR light beam from the source is split into two and passed through the reference and sample
• Both of these beams are now reflected in order to pass through a splitter and then a detector
• After the processor deciphers the data
  passed through the detector, the required reading is printed out

Question 4

What are some of the applications of infrared spectroscopy

Answer 4

• Is widely used in both industry and research
• It is a simple and dependable measurement, quality control, and dynamic measurement technique
• It is also used in forensic analysis, both civil and criminal

The following are some of the most important applications of IR spectroscopy:

1. Identification of functional group and structure elucidation
2. Identification of substances
3. Studying the progress of the reaction
4. Detection of impurities
5. Quantitative analysis

Question 5

What are the disadvantages of IR spectroscopy

Answer 5

• Sample Constraint: Infrared spectroscopy is not applicable to water-containing samples because this solvent absorbs IR light strongly
• Spectrum Complication : The IR spectrum is extremely complicated, and interpretation requires a great deal of experience
• On the basis of a single IR spectrum, we cannot always determine the structure of a compound
• Other spectroscopy techniques, such as Mass Spectrometry (MS) and Nuclear Magnetic Resonance (NMR), are still required to fully understand the specific structure
• Quantification: While infrared spectroscopy is effective for qualitative analysis of a wide range of samples, quantitative analysis may be limited under certain conditions, such as very high and low concentrations

Question 6

What is the principle on which infrared spectroscopy works

Answer 6

• Is based on the idea that molecules absorb specific frequencies that are unique to their structure
• All atoms in molecules are in continuous vibration with respect to each other at temperatures above absolute zero
• A sample’s IR spectrum is recorded by passing an IR radiation beam through it
• When the frequency of a specific vibration equals the frequency of the IR radiation directed at the molecule, the radiation is absorbed
• The amount of energy absorbed at each frequency is revealed by examining the transmitted light (or wavelength)
• IR spectrometers can accept a wide variety of sample types, including gases, liquids, and solids, by using various sampling accessories

Question 7

Explain crystalline solid

Answer 7

• Have particles arranged in regular 3 dimension
• Have a sharp melting point
• Have a definite geometric shape
• True solid
• Symmetrical
• More rigid
• Long range order

eg ) potassium nitrate; copper

Question 8

Explain Schottky defect

Answer 8

• A type of point defect found in ionic crystals where equal numbers of cations and anions are missing from their regular lattice sites
• Atoms permanently leave crystal ( both anion and cation )
• The difference in size between cation and anion is small
• Density decreases because ions are missing
• Electrical neutrality of the crystal remains unchanged
• Formation of 2 vacancies.

Example:
In sodium chloride (NaCl), if one Na⁺ ion and one Cl⁻ ion leave their lattice sites, a Schottky defect is formed

Question 9

Explain amorphous solid

Answer 9

• Have particles arranged in a random or irregular manner with no long-range order
• No particular melting point
• Isotropic
• Unsymmetrical
• Less rigid
• Pseudo solid
• Short range order

eg ) Cellophane ; polyvinyl chloride

Question 10

Explain frenkel defect

Answer 10

• Contains ionic crystals where the anion is larger than the cation
• Usually the smaller ion cation leaves its original lattice structure
• Atoms remain within the solid crystal
• Only one vacancy is created
• Density remains the same