Free Spectroscopy and Analysis MCQs with Answers

1. The process of formation of spectrum is known as:

• A. Diffraction
• B. Interferences
• C. Refraction
• D. Spectroscopy

Explanation: Spectroscopy is like the CSI of light! It's all about studying how light interacts with matter. By analyzing the light that's emitted, absorbed, or scattered, scientists can uncover a wealth of information about the composition, structure, and properties of substances. It's like a magical light language that helps us decode the mysteries of the universe!

2. Spectrum shows the number of component color present in certain light in terms of:

• A. Frequency
• B. Energy
• C. Wavelength
• D. All of the above

Explanation: (a) Frequency: This is like the beat of the light wave, how fast it's waving. Different frequencies give us different colors, like the notes in a rainbow song.(b) Energy: Think of this as the power level of the light wave. Higher energy means bluer light, while lower energy is more on the red end of the spectrum.(c) Wavelength: Picture this as the physical distance between the light wave peaks. Shorter wavelengths mean bluer light, and longer wavelengths mean redder light.So, when we look at the spectrum, we can see all these aspects: the frequency, energy, and wavelength of the light, painting a vibrant picture of the components present in that light. It's like reading a musical score but with colors instead of notes!

3. X-rays are:

• A. Low velocity invisible rays
• B. High velocity invisible rays
• C. High velocity visible rays
• D. Low velocity visible rays

Explanation: X-rays are high-frequency electromagnetic radiations having wavelengths between 0.01-10 nm, way beyond the visible range that is between 400 and 700 nm, which makes them invisible. As they are electromagnetic waves, their velocity is very high.

4. The atomic spectra deals with the measurement of:

• A. Wavelengths
• B. Intensities of electromagnetic radiations emitted by atoms
• C. Intensities of electromagnetic radiations absorbed by atoms
• D. All of these options
• E. Both B and C

Explanation: The correct answer is D: All of these options. Atomic spectra encompass the study of both the wavelengths and the intensities of electromagnetic radiation emitted and absorbed by atoms. When electrons transition between energy levels, they emit or absorb photons, whose characteristics-like wavelength and intensity-can be measured. Options A, B, and C all address partial aspects of these measurements, but the full scope of atomic spectra includes all these components.

5. For the first time in 1914, Henry Moseley used X-rays for the determination of:

• A. Atomic Number
• B. Atomic Mass
• C. Molecular Mass
• D. Equivalent mass

Explanation: In 1914, he observed and measured the X-ray spectra of various chemical elements using diffraction in crystals. Through this, he discovered a systematic relation between wavelength and atomic number. This discovery is now known as Moseley's Law. He found that certain lines in the X-ray spectrum of elements move by the same amount each time when we increase the atomic number by one.

6. The number of peaks given by ethane thiol in the H-NMR spectrum is:

• A. 2
• B. 3
• C. 4
• D. None

Explanation: Ethane thiol has the formula CH3- CH2- SH so the number of peaks of proton NMR are going to be 3

7. In IR spectrum, a strong peak at 1720 cm-1 indicates the presence of:

• A. C = C Bond
• B. C = O Bond
• C. C ≡ N Bond
• D. O - H Bond

Explanation: The carbonyl group (C=O) exhibits a strong absorption band around 1720 cm-1 due to the stretching vibration of the double bond between the carbon and oxygen atoms.

8. Quote the wave length range of IR region

• A. 0.8-2.5μm
• B. 16-1000μm
• C. 2.5-16μm
• D. 400-800μm

Explanation: Here are the approximate wavelength ranges for different portions of the infrared region:Near-infrared (NIR): 0.75 μm to 1.5 μmShort-wavelength infrared (SWIR): 1.5 μm to 3 μmMid-wavelength infrared (MWIR): 3 μm to 8 μmLong-wavelength infrared (LWIR): 8 μm to 15 μmFar-infrared (FIR): 15 μm to 1000 μm (or 1 mm)

9. Mass spectrum of Magnesium shows that it contains three isotopes. Mg-24 (78.70%), Mg-25 (10.13%) & Mg-26(11.17%). The average atomic mass of Mg is

• A. 24.32 amu
• B. 25.32 amu
• C. 26.32 amu
• D. 27.32 amu

Explanation: To calculate the average atomic mass, we use the formula:Average atomic mass=(Abundance1×Atomic mass1)+(Abundance2×Atomic mass2)+(Abundance3×Atomic mass3)Substituting the values:Average atomic mass=(0.7899×23.98504 )+(0.1000×24.98584 )+(0.1101×25.98259 )Average atomic mass=18.99254 +2.49858 +2.86561 Average atomic mass=24.35673 So, the average atomic mass of magnesium is approximately 24.35673

10. Which of the following electronic transitions requires highest amount of energy when a compound is interacted with ultraviolet radiations?

• A. n → Π
• B. Π → Π
• C. 8 → 8
• D. n → 8

Explanation: This transition involves the excitation of an electron from a non-bonding orbital (n) to another orbital (8). If 8 represents a higher energy orbital, this transition could require a significant amount of energy, potentially more than the other transitions listed, depending on the specific molecular orbitals involved.