Chemistry · Physics

Thermodynamics and Chemical Kinetics

1,132 Questions

Thermodynamics and chemical kinetics are crucial branches of physical chemistry. This area focuses on energy transformations, reaction rates, equilibrium constants, and catalysts. These topics carry significant weight in competitive science and engineering examinations.

Enthalpy and energyChemical equilibriumEntropy conceptsReaction kinetics and catalysts

Thermodynamics and Chemical Kinetics Questions

Multiple choice

Which of the following is NOT true for chemical change?

  1. New substance are formed.

  2. No change is mass of substance occurs.

  3. It can not be reversed.

  4. It release or absorb heat or other energy.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In a chemical change, the mass of any individual substance changes

Multiple choice

Which of the following statement is TRUE?

  1. Energy is given out on forming new bond but required for breaking a bond.

  2. Energy is required for forming a new bond but given out for breaking a bond.

  3. Energy is given out while forming or breaking a bond.

  4. Energy is required for forming or breaking a bond.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Energy is required for breaking a bond, but given out when a new bond is formed.

Multiple choice

A conversion process can cause all, except the

  1. change in number of carbon atoms per molecule

  2. change in ratio of molecular hydrogen to carbon

  3. change in the molecular structure

  4. change in the percentage of halogen
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Conversion processes in petroleum refining change carbon numbers (cracking), hydrogen-to-carbon ratios (reforming), and molecular structures (isomerization). However, halogen content is not typically altered in these processes as halogens are not naturally occurring components in crude oil that would be modified during conversion.

Multiple choice

Which of the following statements is TRUE about chemical reactions?

  1. All chemical reactions are reversible.

  2. All chemical reactions release heat during decomposition of molecules.

  3. Each chemical reaction is carried out by breaking bond between the molecules.

  4. All chemical reactions do not burn and dissolve.

  5. All of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Chemists are concerned with both physical and chemical change, and the energy associated with each. Chemical reactions involve the making and breaking of covalent bonds and these transformations have energy consequences.The sum of all the bond energies of a molecule can therefore be considered its atomization energy, i.e. the energy required to break the molecule completely into its component atoms.

Multiple choice

A chemical, when burned, produces energy if

  1. the energy absorbed by reactants is more than the energy released by products

  2. the energy absorbed by reactants is less than the energy released by products

  3. the energy released by products is equal to energy absorbed by reactants

  4. it reacts with carbon dioxide

  5. none of these

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Yes, when the energy absorbed by reactants is less than energy released by products.

Multiple choice

Enzymes act on the substrate in several ways, except by

  1. lowering the energy of the transition state of the substrate

  2. increasing the reaction entropy change

  3. providing an alternative pathway

  4. lowering the activation energy
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

They reduce the reaction entropy change by bringing substrates together in the correct orientation to react. Considering ΔH‡ alone overlooks this effect.

Multiple choice

Which of the following statements is incorrect? A. βn is equal to the product of K1, K2, K3 …… Kn. B. K1, K2, K3 …… Kn are called stepwise stability or formation constants. C. βn = K1 + K2 + K3 …… Kn.

  1. Only A

  2. Only B

  3. Only C

  4. A and B

  5. A and C
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This is correct because the overall stability constant (βn) is equal to the product of stepwise stability constants K1, K2, K3 ……Kn, i.e.,  βn = K1 ˣ K2 ˣ K3 ……Kn.

Multiple choice

The Ellingham diagram cannot tell

  1. about the speed of reaction

  2. about the feasibility of a reaction

  3. about which substance is a better reducing agent

  4. about the thermodynamic concept of a reaction
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Ans : 1.

Multiple choice

Entropy means

  1. disorder

  2. heat

  3. free energy

  4. enthalpy
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Ans : 1.

Multiple choice

Free energy charge is

  1. inversely related to rate constant

  2. directly related to rate constant

  3. directly related to negative value of rate constant

  4. directly related to minus log of rate constant
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Ans : 4.

Multiple choice

Which of the following forces/ effects is used to describe the potential energy of the system in molecular modeling?

  1. Force field

  2. Hydrophobic effect

  3. Intramolecular force

  4. Polarizability

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the context of molecular modeling, a force field refers to the form and parameters of mathematical functions used to describe the potential energy of a system of particles (typically molecules and atoms). Force field functions and parameter sets are derived from both experimental work and high-level quantum mechanical calculations.