This set of Analytical Instrumentation Multiple Choice Questions & Answers (MCQs) focuses on “Instrumentation of IR”.
1. Which of the following is not a source used in Mid Infrared Spectrophotometer? a) Nernst glower b) High pressure mercury arc lamp c) Globar d) Nichrome wire View AnswerAnswer: b Explanation: High pressure mercury arc lamp is used as the source for Far IR Spectrophotometer. Rest of the options are used as a source in Mid Infrared Spectrophotometer.
2. Which of the following is the wave number of near infrared spectrometer? a) 4000 – 200 cm-1 b) 200 – 10 cm-1 c) 12500 – 4000 cm-1 d) 50 – 1000 cm-1 View AnswerAnswer: c Explanation: The wave number of near infrared spectrometer ranges between 12500 – 4000. Wavenumber is the reciprocal of wavelength.
3. Which of the following options are correct in terms of wavelength for the different types of IR spectrometer? a) Near IR: 0.8 – 2.5 mm b) Mid IR: 0.8 – 2.5 mm c) Far IR: 2.5 – 50 mm d) Mid IR: 50 – 100 mm View AnswerAnswer: a Explanation: Wavelength of near IR is 0.8 – 2.5 mm and for mid IR it is 2.5 – 50 mm. The wavelength of far IR is 50 – 1000 mm.
4. Which of the following is not a composition of Nernst glower or Nernst filament? a) Oxides of Zirconium b) Oxides of Barium c) Oxides of Yitrium d) Oxides of Thorium View AnswerAnswer: b Explanation: Oxides of Barium is not present in Nernst glower. They are constructed by fusing oxides of Zirconium, yitrium and thorium.
5. What is the composition of Globar rod which is used as a source in Mid IR spectroscopy? a) Silicon carbide b) Silver chloride c) Silicon dioxide d) Silver carbide View AnswerAnswer: a Explanation: Globar is a silicon carbide rod. It is 5mm in diameter and 50mm long.
6. Bolometer, a type of detector, is also known as ___________ a) Resistance temperature detector (RTD) b) Thermistor c) Thermocouple d) Golay cell View AnswerAnswer: b Explanation: Bolometers are also known as thermistors. It is a type of resistance thermometer constructed of metals such as platinum or nickel.
7. Which of the following is not a technique for preparing solid samples in IR spectroscopy? a) Solids run in solution b) Mull technique c) Solid films d) Thin films View AnswerAnswer: d Explanation: Four techniques are generally used to prepare solid samples. They are: Solids run in solution, Mull technique, Solid films and pressed pellet techniques.
8. Which of the following is not used as pyroelectric material used in pyroelectric transducers in Infrared spectroscopy? a) Triglycine Sulphate b) Deutrated Triglycine Sulphate c) Some Polymers d) Tetraglycine sulphate View AnswerAnswer: d Explanation: Pyroelectric materials are deutrated triglycine sulphate, triglycine sulphate and some polymers. They give rise to potential when subjected to a heating or cooling effect.
9. Which of the following is the principle of Golay cell which is used as a detector in IR spectroscopy? a) Expansion of gas upon heating b) Increase in resistance due to an increase in temperature and vice versa c) Temperature difference gives rise to a potential difference in the material d) Decrease in resistance due to an increase in temperature View AnswerAnswer: a Explanation: It is also known as pneumatic detector. The gases expand on heating and this in turn leads to the movement of a diaphragm just like in pneumatic sensors.
10. In a solid sample treatment technique, the finely ground solid sample is mixed with mineral oil to make a thick paste which is then spread between IR transmitting windows. What is the name of this solid sample treatment technique? a) Pressed pellet b) Mull technique c) Solid films d) Solids run in solution View AnswerAnswer: b Explanation: The mentioned technique is Mull technique. This method is used for qualitative analysis but not quantitative analysis.
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Infrared Spectroscopy in Chemistry Questions with Solutions
Q1. Which of the following statements about infrared spectroscopy is correct?
a.) When the frequency of infrared light matches the frequency of bond vibration in a molecule, a peak appears on the spectrum.
b.) Infrared spectroscopy can be used to determine the size and shape of a compound’s carbon skeleton.
c.) An IR spectrometer illuminates a compound with infrared light and records the positions where the light is blocked by the compound. This results in the peaks of the spectrum.
d.) The fingerprint region of the spectrum can be used to identify functional groups.
Correct Answer – a.) When the frequency of infrared light matches the frequency of bond vibration in a molecule, a peak appears on the spectrum.
Q2. In an infrared (IR) spectrum, which of the following functional groups has the highest frequency?
Correct Answer – d.) Alcohol.
Q3. A carbonyl group will cause a sharp dip at about ____ cm–1.
Correct Answer – (a.) 1700
Q4. Which of the following causes the vibration of atoms?
a.) The number of protons contained in a nucleus.
b.) Electron movement to higher energy levels.
c.) The molecule’s total molecular weight.
d.) Dipole moments between atoms.
Correct Answer – d.) Dipole moments between atoms.
Q5.What is the range of the infrared spectrum?
Answer – The infrared spectrum extends from 700 to 1000 nm (wavelength), or 14,286 to 12,800 cm–1 (wavenumber).
Q6. What is the fundamental measurement in IR spectroscopy?
Answer – An infrared spectrum is a plot between measured infrared intensity versus wavelength (or frequency) of light, which is the fundamental measurement obtained in infrared spectroscopy.
Q7. Which solvent is ideal for infrared spectroscopy?
Answer – Carbon Tetrachloride (CCl4) and Carbon Disulfide (CS2) are the most commonly used solvents. Polar materials can be dissolved in chloroform, methylene chloride, acetonitrile, and acetone.
Q8. What are the different types of infrared spectroscopy?
Answer – The two types of infrared spectrometers are:
Q9. What is the region of the infrared spectrum?
Answer – The majority of the bands that indicate which functional group is present are found between 4000 cm–1 and 1300 cm–1. Their bands can be identified and used to determine the functional group of an unknown compound functional group.
The fingerprint region, from 1300 cm–1 to 400 cm–1, contains bands that are unique to each molecule, similar to a fingerprint. These bands are only used to compare the spectra of different compounds.
Q10. How does infrared spectroscopy work?
Answer – Infrared (IR) spectroscopy 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.
Q11. What is the necessary condition for IR spectroscopy?
Answer – 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.
Q12. How does the IR spectroscopy instrument work?
Answer – The infrared spectroscopy instrumentation is shown below.
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.
Q13. What are some of the applications of infrared spectroscopy?
Answer – Infrared spectroscopy 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:
Q14. What is the principle on which infrared spectroscopy works?
Answer – IR spectroscopy 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.
Q15. What are the disadvantages of IR spectroscopy?
Answer – The disadvantages of IR spectroscopy are:
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4. Which of the following is not a composition of Nernst glower or Nernst filament? a) Oxides of Zirconium b) Oxides of Barium c) Oxides of Yitrium d) Oxides of Thorium View AnswerAnswer: b Explanation: Oxides of Barium is not present in Nernst glower. They are constructed by fusing oxides of Zirconium, yitrium and thorium.
This set of Analytical Instrumentation Multiple Choice Questions & Answers (MCQs) focuses on “Instrumentation of IR”.
10. In a solid sample treatment technique, the finely ground solid sample is mixed with mineral oil to make a thick paste which is then spread between IR transmitting windows. What is the name of this solid sample treatment technique? a) Pressed pellet b) Mull technique c) Solid films d) Solids run in solution View AnswerAnswer: b Explanation: The mentioned technique is Mull technique. This method is used for qualitative analysis but not quantitative analysis.
9. Which of the following is the principle of Golay cell which is used as a detector in IR spectroscopy? a) Expansion of gas upon heating b) Increase in resistance due to an increase in temperature and vice versa c) Temperature difference gives rise to a potential difference in the material d) Decrease in resistance due to an increase in temperature View AnswerAnswer: a Explanation: It is also known as pneumatic detector. The gases expand on heating and this in turn leads to the movement of a diaphragm just like in pneumatic sensors.
5. What is the composition of Globar rod which is used as a source in Mid IR spectroscopy? a) Silicon carbide b) Silver chloride c) Silicon dioxide d) Silver carbide View AnswerAnswer: a Explanation: Globar is a silicon carbide rod. It is 5mm in diameter and 50mm long.
IR spectroscopy interview question and answers most common interview Question and answer
FAQ
Why is KBr used in IR spectroscopy?
The IR spectroscopy theory utilizes the concept that molecules tend to absorb specific frequencies of light that are characteristic of the corresponding structure of the molecules.
What are the two main applications of IR spectroscopy?
What techniques are used in IR spectroscopy?
- Identification of functional group and structure elucidation.
- Identification of substances. …
- Studying the progress of the reaction.
- Detection of impurities.
- Quantitative analysis.
