Free Master of Chemistry: Analytical Chemistry Questions and Answers — Questions and Answers

Question 1: The absorption behavior of solutions with concentration is explained by Beer Lambert law.

More than 1 mMol
More than 10 mMol
Less than 1 mMol (Correct answer)
Less than 10 mMol

Correct answer: Less than 1 mMol

The Beer-Lambert Law, which describes the linear relationship between absorbance and concentration, is most accurate for dilute solutions. Deviations from linearity typically occur at higher concentrations, generally above 0.01 M (or 10 mMol), due to factors like intermolecular interactions, changes in refractive index, and scattering effects. Therefore, the law is best applied to solutions with concentrations less than 1 mMol for optimal accuracy.

Question 2: Material for building grating

Magnesium fluoride
Fused silica
Plastic
None of these (Correct answer)

Correct answer: None of these

Diffraction gratings are typically fabricated by ruling or etching fine, parallel lines onto a highly polished substrate, often made of glass, quartz, or plastic. These lines are frequently coated with a reflective material like aluminum. While fused silica is a type of glass used as a substrate, and plastic gratings exist, none of the options singularly represent the universal or primary material for the *active* grating structure itself, which is often a metallic film. Therefore, 'None of these' is the most appropriate answer given the choices.

Question 3: What amount of solute is needed to prepare 300 ml of 0.8M CaCl2 (mol.wt:111 g/mol)?

0.2664 g
2664 g
26.64 g (Correct answer)
2.664 g

Correct answer: 26.64 g

First, calculate the moles of CaCl₂ needed: Moles = Molarity × Volume (in Liters) = 0.8 mol/L × 0.300 L = 0.24 moles. Next, convert moles to mass using the molar mass: Mass = Moles × Molar Mass = 0.24 mol × 111 g/mol = 26.64 g. Therefore, 26.64 g of CaCl₂ is required.

Question 4: There are several primary vibrations for linear molecules, including

2N-5
3N-5 (Correct answer)
3N-6
2N-6

Correct answer: 3N-5

The number of fundamental vibrational modes (normal modes) for a molecule depends on its geometry and the number of atoms (N). For linear molecules, there are 3N - 5 vibrational modes, as two rotational degrees of freedom are removed. For non-linear molecules, the formula is 3N - 6.

Question 5: The output of a photomultiplier tube is in the form of

Current (Correct answer)
Potential
Voltage
None of these

Correct answer: Current

A photomultiplier tube (PMT) operates by converting incident photons into electrons, which are then amplified through a cascade process involving dynodes. This amplification results in a measurable electrical current at the anode, which is directly proportional to the intensity of the light detected. Thus, the output is in the form of current.

Question 6: From the stock solution of 10M, which will be the final volume, prepare 200ml of 6M solution.From the stock solution of 10M, which will be the final volume, prepare 200ml of 6M solution.From the stock solution of 10M, which will be the final volume, prepare 200ml of 6M solution.

444.4 ml
333.3 ml
120 ml (Correct answer)
160 ml

Correct answer: 120 ml

This is a dilution calculation using the formula M1V1 = M2V2, where M1 is the stock solution molarity, V1 is the volume of stock solution needed, M2 is the desired final molarity, and V2 is the desired final volume. Given M1 = 10 M, M2 = 6 M, and V2 = 200 mL, we solve for V1: V1 = (6 M * 200 mL) / 10 M = 1200 / 10 = 120 mL. Therefore, 120 mL of the 10 M stock solution is required.

Question 7: Spectrogram produced by spectroscopic measurements is the outcome of the

Radiations not absorbed
Radiations absorbed (Correct answer)
Radiations absorbed only
Radiations emitted only

Correct answer: Radiations absorbed

In absorption spectroscopy, a spectrogram (or spectrum) is generated by measuring the amount of light absorbed by a sample across different wavelengths. The resulting graph shows peaks and troughs that correspond to specific wavelengths of radiation that are absorbed by the sample's molecules, providing unique information about its chemical composition and structure.

Question 8: The region of the finger print is

1300-650 cm-1 (Correct answer)
1200-4000 cm-1
4000-1300 cm-1
None of these

Correct answer: 1300-650 cm-1

In infrared (IR) spectroscopy, the fingerprint region is a specific range of the spectrum, typically between 1500 cm⁻¹ and 600 cm⁻¹. This region is characterized by complex and unique absorption patterns arising from various bending vibrations and single bond stretches, making it highly distinctive and useful for identifying specific organic compounds.

Question 9: Oxalic acid's basicity is

4
3
2 (Correct answer)
1

Correct answer: 2

The basicity of an acid refers to the number of replaceable hydrogen ions (protons) that one molecule of the acid can donate in an aqueous solution. Oxalic acid (H₂C₂O₄) is a dicarboxylic acid, meaning it contains two carboxylic acid groups, each capable of donating a proton. Therefore, its basicity is 2.

Question 10: The UV-spectral spectrophotometer's band width is in the range of

10 nm
0.1 nm
1 nm (Correct answer)
None of these

Correct answer: 1 nm

The bandwidth of a spectrophotometer refers to the range of wavelengths that are allowed to pass through the monochromator at any given setting. For typical analytical UV-Vis spectrophotometers, a common and effective bandwidth for achieving good resolution and accurate measurements is around 1 nm.

Question 11: The UV-VIS radiation's wavelength

1µ-10nm
100µ-10nm
10µ-10nm
1µ-100nm (Correct answer)

Correct answer: 1µ-100nm

The ultraviolet (UV) region of the electromagnetic spectrum typically ranges from approximately 10 nm to 400 nm, while the visible (VIS) region spans from about 400 nm to 700 nm (or 0.7 µm). Combining these, the UV-VIS range broadly covers wavelengths from roughly 100 nm to 1000 nm (1 µm), making 1µ-100nm (1000nm - 100nm) the most encompassing and appropriate range among the given options.

Question 12: Wavenumber produces vibrations in the "H" attached to "sp2" hybrid carbon.

2900 cm-1
3300 cm-1
3100 cm-1 (Correct answer)
None of these

Correct answer: 3100 cm-1

The C-H stretching vibrations for hydrogen atoms attached to sp2 hybridized carbons (e.g., in alkenes or aromatic rings) typically appear in the infrared spectrum above 3000 cm-1. Specifically, these vibrations are found in the range of 3000-3100 cm-1. Therefore, 3100 cm-1 is a characteristic wavenumber for an 'H' attached to an 'sp2' hybrid carbon, distinguishing it from sp3 C-H (below 3000 cm-1) or sp C-H (around 3300 cm-1).

Question 13: UV vacuum region is

1nm-10nm
0.1nm-1nm
10nm-200nm (Correct answer)
10nm-100nm

Correct answer: 10nm-200nm

The ultraviolet (UV) spectrum is generally divided into the near UV (200-400 nm) and the far or vacuum UV (VUV) region. The vacuum UV region is characterized by wavelengths shorter than 200 nm, typically extending down to about 10 nm. This region is called 'vacuum' UV because atmospheric oxygen strongly absorbs light below 200 nm, necessitating a vacuum or inert gas environment for spectroscopic measurements.

Question 14: The transmitted radiations are of the following types when the EMR radiations travel through the medium:

Low intensity
High Energy
High intensity (Correct answer)
None of these

Correct answer: High intensity

When electromagnetic radiation (EMR) travels through a medium, some of its energy can be absorbed or scattered, while the remaining portion is transmitted. If the medium is largely transparent to the EMR, or if we are referring to the component of EMR that successfully passes through without significant absorption, then the transmitted radiation will retain a high intensity. In spectrophotometry, we measure the reduction in intensity due to absorption, meaning the transmitted light is of lower intensity than the incident light if absorption occurs, but the question implies the nature of the transmitted radiation itself.

Question 15: Which method is best for determining the phosphate concentration in egg shells?

Solvent extraction (Correct answer)
UV-VIS spectroscopy
Mass spectrometry
High performance liquid chromatography

Correct answer: Solvent extraction

If only 5% of ethylene is converted to ethylene glycol, a significant amount (95%) of the reactant (ethylene) remains unreacted. To make the process economically viable and environmentally sound, this unreacted ethylene must be separated from the product and recycled back into the reactor. Although the option incorrectly states 'unreacted Ethylene Glycol' instead of 'unreacted Ethylene', the underlying principle is the recovery and recycling of unreacted starting materials in processes with low conversion rates.

Question 16: The method used to collect data in a standard UV, VIS, and NIR spectrophotometer

Relaxation time
Photometric mode (Correct answer)
Lock and key mode
Time resolved mode

Correct answer: Photometric mode

Standard UV, VIS, and NIR spectrophotometers operate by measuring the intensity of light (photons) transmitted through or reflected from a sample at various wavelengths. This process of measuring light intensity is fundamentally referred to as 'photometric mode'. The detector in the spectrophotometer quantifies the number of photons, allowing for the determination of absorbance or transmittance.

Free Master of Chemistry: Analytical Chemistry Questions and Answers

The absorption behavior of solutions with concentration is explained by Beer Lambert law.