Chemical Science MCQs: Previously asked problems in CSIR NET Chemical Science

Chemical Science MCQs previously asked problems in CSIR NET CHEMICAL SCIENCE Which of the following is not a correct statement about molecular mechanics method?
It calculates the potential energy of a molecule by taking into account only the bonds and angles between atoms.
It is a classical mechanics method that uses an empirical potential energy function to evaluate the molecular energy.
It is a quantum mechanics method that solves the Schrödinger equation for the molecule to obtain its energy levels.
It can be used to optimize the geometry of a molecule by minimizing its potential energy.

Answer: It is a quantum mechanics method that solves the Schrödinger equation for the molecule to obtain its energy levels.

Which of the following is not a correct statement about the Born-Haber cycle?
It is a thermodynamic cycle that relates the lattice energy of an ionic solid to other thermodynamic quantities such as enthalpy of formation and ionization energies.
It can be used to calculate the lattice energy of an ionic solid from experimental data.
It is based on the principle of Hess's law, which states that the total enthalpy change of a reaction is independent of the pathway taken.
It is a quantum mechanical method that calculates the electron density of an ionic solid.

Answer: It is a quantum mechanical method that calculates the electron density of an ionic solid.

Which of the following is not a correct statement about the Marcus theory of electron transfer?
It is a theory that describes electron transfer reactions between two species, such as a donor and an acceptor.
It is based on the assumption that the reactants and products are in thermodynamic equilibrium.
It predicts the rate of electron transfer based on the reorganization energy and the free energy change of the reaction.
It is a classical mechanics method that solves the equations of motion for the electrons and nuclei in the system.

Answer: It is a classical mechanics method that solves the equations of motion for the electrons and nuclei in the system.

Which of the following is not a correct statement about NMR spectroscopy?
It is a spectroscopic technique that uses the magnetic properties of atomic nuclei to determine the structure of a molecule.
It can be used to determine the number and types of atoms in a molecule, as well as their spatial arrangement.
It is based on the principle of energy absorption and emission by atomic nuclei in a magnetic field.
It can only be used for molecules that contain paramagnetic atoms, such as iron or copper.

Answer: It can only be used for molecules that contain paramagnetic atoms, such as iron or copper.

Which of the following is not a correct statement about the Woodward-Hoffmann rules?
They are a set of rules that predict the stereochemistry of thermal pericyclic reactions, such as [4+2] and [2+2] cycloadditions.
They are based on the conservation of orbital symmetry and the allowed or forbidden nature of certain molecular orbitals interactions.
They were first proposed by Robert Burns Woodward and Roald Hoffmann in the 1950s.
They are only applicable to reactions that involve molecules with conjugated double bonds.

Answer: They are only applicable to reactions that involve molecules with conjugated double bonds.

Which of the following is not a correct statement about the Boltzmann distribution?
It is a statistical distribution that describes the distribution of energy among particles in a system at thermal equilibrium.
It is based on the assumption that the particles in the system have discrete energy levels.
It predicts that the most probable energy state of a particle is the one with the highest energy.
It can be used to calculate the equilibrium constant of a chemical reaction.

Answer: It predicts that the most probable energy state of a particle is the one with the highest energy.

Which of the following is not a correct statement about the Born-Haber cycle?
It is a cycle of reactions that describes the formation of an ionic compound from its constituent elements.
It includes energies of ionization, electron affinities, and lattice energies.
It can be used to calculate the enthalpy of formation of an ionic compound.
It does not involve the calculation of the activation energy of the reaction.

Answer: It does not involve the calculation of the activation energy of the reaction.

Which of the following is not a correct statement about electrochemistry?
It is the study of the relationship between electricity and chemical reactions.
It involves the measurement of electrical properties, such as potential and current, in chemical systems.
It includes the study of redox reactions and the calculation of electrode potentials.
It does not have any practical applications in industry or technology.

Answer: It does not have any practical applications in industry or technology.

Which of the following is not a correct statement about NMR spectroscopy?
It is a technique that uses the magnetic properties of atomic nuclei to determine the chemical structure of a compound.
It can be used to determine the stereochemistry of a compound.
It is based on the principle of nuclear spin and the interaction of atomic nuclei with an external magnetic field.
It is a technique that can only be used for the analysis of small organic molecules.

Answer: It is a technique that can only be used for the analysis of small organic molecules.

Which of the following is not a correct statement about mass spectrometry?
It is a technique that can be used to determine the molecular weight of a compound.
It involves ionizing a sample, separating the ions based on their mass-to-charge ratio, and detecting the ions to generate a mass spectrum.
It can be used to identify the chemical formula of a compound.
It can only be used to analyze compounds that are volatile and thermally stable.

Answer: It can only be used to analyze compounds that are volatile and thermally stable.

Which of the following statements about NMR spectroscopy is correct?
It can be used to determine the molecular structure and connectivity of a compound.
It involves the absorption of electromagnetic radiation by nuclei in a magnetic field.
The chemical shift observed in an NMR spectrum is influenced by the electron density around the nucleus being examined.
All of the above.

Answer: All of the above.

Which of the following reagents is commonly used for the reduction of aldehydes and ketones to alcohols?
Sodium borohydride (NaBH4).
Lithium aluminum hydride (LiAlH4).
Hydrazine (N2H4).
Borane (BH3).

Answer: Lithium aluminum hydride (LiAlH4).

Which of the following statements about a reaction's rate constant is true?
It is a measure of how fast the reaction proceeds.
It is dependent on the activation energy of the reaction.
It is temperature-dependent.
All of the above.

Answer: All of the above.

Which of the following statements about electrochemistry is correct?
The anode is the site of reduction in an electrochemical cell.
The cathode is the site of oxidation in an electrochemical cell.
The standard electrode potential is the measure of the tendency of an electrode to lose or gain electrons.
All of the above.

Answer: The standard electrode potential is the measure of the tendency of an electrode to lose or gain electrons.

Which of the following statements about carboxylic acids is true?
They have a hydroxyl (-OH) group attached to a carbonyl group (C=O).
They are typically weak acids, with pKa values in the range of 4-5.
They can undergo nucleophilic acyl substitution reactions with nucleophiles such as amines and alcohols.
All of the above.

Answer: They are typically weak acids, with pKa values in the range of 4-5.

Which of the following is a correct statement about the Hückel rule?
It states that aromatic compounds must contain an odd number of pi electrons in a planar, cyclic, and fully conjugated system.
It states that antiaromatic compounds must contain an even number of pi electrons in a planar, cyclic, and fully conjugated system.
It can be used to predict the aromaticity or antiaromaticity of a compound based on its structure and electron count.
All of the above.

Answer: It can be used to predict the aromaticity or antiaromaticity of a compound based on its structure and electron count.

Which of the following is a correct statement about nucleophilic substitution reactions?
In an SN1 reaction, the rate-determining step is the attack of the nucleophile on the substrate.
In an SN2 reaction, the nucleophile attacks the substrate at the same time that the leaving group leaves.
Steric hindrance around the substrate can slow down or prevent nucleophilic substitution reactions from occurring.
All of the above.

Answer: Steric hindrance around the substrate can slow down or prevent nucleophilic substitution reactions from occurring.

Which of the following is a correct statement about transition metal complexes?
The coordination number of a transition metal complex refers to the number of metal-ligand bonds in the complex.
A chelating ligand can bind to a metal ion through multiple donor atoms to form a more stable complex.
In a square planar complex, the metal ion is coordinated to four ligands in the same plane, with bond angles of 90 degrees.
All of the above.

Answer: A chelating ligand can bind to a metal ion through multiple donor atoms to form a more stable complex.

Which of the following is a correct statement about enzyme kinetics?
The Michaelis-Menten equation describes the relationship between the substrate concentration and the rate of an enzyme-catalyzed reaction.
The turnover number of an enzyme refers to the maximum number of substrate molecules that can be converted to product per unit time by a single enzyme molecule.
Competitive inhibitors bind to the active site of an enzyme and prevent substrate binding, while noncompetitive inhibitors bind to a different site and change the enzyme's shape and activity.
All of the above.

Answer: The Michaelis-Menten equation describes the relationship between the substrate concentration and the rate of an enzyme-catalyzed reaction.

Which of the following is a correct statement about mass spectrometry?
In a mass spectrometer, ions are separated based on their charge-to-mass ratio in a magnetic field.
Electrospray ionization is a soft ionization technique that is commonly used to analyze large biomolecules such as proteins and peptides.
In matrix-assisted laser desorption/ionization (MALDI), the sample is mixed with a matrix compound and then irradiated with a laser, causing the sample to ionize and desorb from the surface of the matrix.
All of the above.

Answer: Electrospray ionization is a soft ionization technique that is commonly used to analyze large biomolecules such as proteins and peptides.

Electron ionization (EI) is a "hard" ionization technique that is commonly used in gas chromatography-mass spectrometry (GC-MS) analysis.
Electrospray ionization is a soft ionization technique that is commonly used to analyze large biomolecules such as proteins and peptides.
In matrix-assisted laser desorption/ionization (MALDI), the sample is mixed with a matrix compound and then irradiated with a laser, causing the sample to ionize and desorb from the surface of the matrix.
All of the above.

Answer: Electrospray ionization is a soft ionization technique that is commonly used to analyze large biomolecules such as proteins and peptides.