Chemistry · Physics

Thermodynamics and Chemical Kinetics

1,092 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

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

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.

Multiple choice

Which of the following does not characterise chemical adsorption?

  1. The heat of adsorption is low.

  2. It is specific in nature.

  3. It increases with increase in temperature.

  4. Only single layer adsorption is possible.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Due to strong chemical bonds formed between adsorbent and adsorbate, the heat of adsorption is generally high.

Multiple choice

Which of the following statements is wrong regarding the catalysts?

  1. The catalyst is generally specific in nature

  2. The catalyst cannot change the position of equilibrium

  3. The catalyst cannot initiate the reaction

  4. Needed in large quantities
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A small quantity of the catalyst is generally sufficient to catalyse a reaction.  (i) For example, in the decomposition of hydrogen peroxide, one gram of colloidal platinum can catalyse 108 litres of hydrogen peroxide.

Multiple choice

The transition state of a catalyzed reaction is

  1. enzyme bound and very slow in the presence of catalyst

  2. lower in energy than that of an uncatalyzed reaction

  3. higher in energy than that of an uncatalyzed reaction

  4. lower in energy than the reaction substrate
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Enzymes catalyze reactions by lowering the activation energy required to reach the transition state. This means the transition state in a catalyzed reaction is energetically more favorable (lower in energy) compared to an uncatalyzed reaction. However, the transition state still has higher energy than both the substrate and product.

Multiple choice

Gibbs free energy is negative in a/an

  1. endergonic reaction

  2. metamorphic reaction

  3. exergonic reaction

  4. isodesmic reaction
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

An exergonic reaction is a chemical reaction where the change in the Gibbs free energy is negative, indicating a spontaneous reaction.

Multiple choice

When one mole of matter is transformed from one form into another under standard conditions, the enthalphy of reaction is termed as

  1. the standard enthalpy change of formation

  2. the standard enthalpy change of combustion

  3. the standard enthalpy of reaction

  4. the standard enthalpy of neutralisation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The standard enthalpy of reaction is the enthalpy change that occurs in a system when one mole of matter is transformed by a chemical reaction under standard conditions.