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 enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

Decrease in activation energy is due to :

  1. an increase in the reactant concentration

  2. an increase in the temperature

  3. a decrease in pressure

  4. catalysts
  5. $\displaystyle pH$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Catalysis is the increase in the rate of a chemical reaction due to the participation of an additional substance called a catalyst. With a catalyst, reactions occur faster and require less activation energy. Because catalysts are not consumed in the catalyzed reaction, they can continue to catalyze the reaction of further quantities of reactant. Often only tiny amounts are required

Multiple choice physics energy management solar power plant production of electricity from solar energy solar equipment solar energy and its applications

In a steady state process, which of the following quantity remains constant throughout the process

  1. Enthalpy

  2. Entropy

  3. Temperature and heat both

  4. Internal energy
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A steady state is a state which remains the same over given time period. In heat transfer problems if there is specific rate of heat transfer through medium (for conduction or convection) and if it remains constant at any time then it is said to have steady state heat transfer. In steady state, there may be different temperatures in body at different locations but the temperature at any given point will remain constant. If the temperature at all locations is same then it is uniform.

n a steady state process, Internal energy is quantity remains constant throughout the process

Multiple choice chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

Selection of temperature to carry out a reduction process depends so as to make:

  1. $\Delta G$ negative
  2. $\Delta G$ positive
  3. $\Delta H$ negative
  4. $\Delta H$ positive
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When $\Delta$G is negative, a process or chemical reaction proceeds spontaneously in the forward direction and similar condition is required for a reduction process also. 

Multiple choice zoology meaning of life energy flow and loss energy flow in a food chain energy flows

One way cycle is

  1. CO$ _2$ cycle
  2. H$ _2$O cycle

  3. Free energy cycle
  4. O$ _2$ cycle
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Free energy cycle is the unidirectional cycle in our ecosystem. In other cycles like oxygen cycle, carbon dioxide cycle and water cycle, the basic elements are circulated and cycled whereas, in free energy cycle, energy flows from solar energy to producers and then consumers to decomposers. 


Multiple choice chemistry adsorption and colloids adsorption theory of heterogeneous catalysis enzymes and catalysts catalysis

The lowering of activation energy by catalyst is due to

  1. formation of adsorbed activated complex and to provide new pathway to reaction

  2. adsorption is always exothermic

  3. the adsorbed activated complex possesses lower energy level than simple activated complex

  4. all the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The lowering of activation energy by catalyst is due to formation of adsorbed activated complex and to provide new pathway to reaction.

Multiple choice chemistry adsorption and colloids adsorption theory of heterogeneous catalysis enzymes and catalysts catalysis

According to adsorption theory of catalysis, the reaction rate increases, because:

  1. Adsorption produces heat which increases the rate of reaction

  2. In the process of adsorption, the kinetic energy of the molecules increases

  3. The concentration of reactants at the active centres becomes high due to adsorption

  4. The activation energy of the reaction becomes high due to adsorption
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Adsorption increases the reaction rate by concentrating reactant molecules on the surface of the catalyst, which increases the frequency of effective collisions. This is the fundamental principle of surface catalysis.

Multiple choice chemistry adsorption and colloids adsorption theory of heterogeneous catalysis enzymes and catalysts catalysis

According to adsorption theory of catalysis, the speed of reaction increases because:

  1. the concentration of the reactant molecules at the active centres of the catalyst becomes high due to adsorption

  2. in the process of adsorption, the activation energy of the molecules becomes large

  3. adsorption produces heat which increases the speed of the reaction

  4. adsorption lowers the activation energy of the reaction
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

According to adsorption theory of catalysis, the speed of reaction increases because the concentration of the reactant molecules at the active centres of catalyst becomes high due to adsorption.

Hence option A is correct.

Multiple choice chemistry adsorption and colloids adsorption theory of heterogeneous catalysis enzymes and catalysts catalysis

According to the adsorption theory of catalysis,the speed of the reaction increase because :

  1. The concentration of reactant molecules at the active centers of the catalyst becomes high due to adsorption

  2. In the process of adsorption, the activation energy of the molecules becomes large

  3. Adsorption produces heat which increases the speed of the reaction

  4. Adsorption lowers the activation energy of the reaction.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The correct answer is $D$ . In the presence of catalyst the speed of reaction increases since the activation energy gets reduced and hence the rate of adsorption increases.

Multiple choice biology classification of living organisms binomial nomenclature nomenclature of organisms naming of the organisms nomenclature in classification

Which is correct about energy changes in living cells?

  1. First energy transfer, then energy transformation

  2. First energy transformation, then energy transfer

  3. Both occur discontinuously

  4. Both occur continuously
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The chemical energy from the organic molecules is transformed into a simpler form by cells through cellular respiration (Energy Transformation) and then transferred to other tissues of the body for their metabolic activities (Energy transfer). Both these processes happen continuously in our body.

The correct answer is D.

Multiple choice physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy production of electricity from solar energy

There will be an increase in potential energy of the system if work is done upon the system by

  1. any conservative or non-conservative forces

  2. a non-conservative force

  3. conservative force

  4. None of the these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Since potential energy defined only for conservative force. It will increase for conservative force.

Multiple choice chemistry energy rocks and minerals petroleum and natural gas fossil fuels

In a case of catalytic reforming dehydration of naphthenes to aromatics is:

  1. favoured by a decrease in temperature and decrease in pressure

  2. favoured by an increase in temperature and increase in pressure

  3. favoured by an increase in temperature and decrease in pressure

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In catalytic reforming process, high octane number reformate is formed which is the main component of the motor, fuel, aviation gasoline or aromatic rich feedstock. Favourable Conditions for the reaction are High temperature, Low pressure and low space velocity.

Multiple choice chemistry energy rocks and minerals petroleum and natural gas fossil fuels

With increase in octane number:

  1. cetane number decreases

  2. activation energy increases

  3. both A & B

  4. neither A nor B
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Higher is the octane number higher is the activation energies. Activation energy is the amount of energy required to initiate combustion. 

Cetane number is the fuel's eagerness to ignite from the heat created in the bore from the compression of the air. Higher is the cetane number lower is the octane number.

Multiple choice chemistry energy rocks and minerals petroleum and natural gas fossil fuels

The activity of the catalyst in a semi-regenerative catalytic reformer is reduced over time during operation by:

  1. chloride loss

  2. carbonaceous coke

  3. both A and B together

  4. either A or B
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In catalytic reforming process, the noble metals platinum and rhenium are the catalysts used on a silica or silica-alumina support base. Fresh catalyst is chlorinated prior to use. On the other hand, an excessive chlorination could depress excessively the activity of the catalyst. Also in the case of the semi-regenerative catalytic reformer, the catalyst is reduced over time by carbonaceous coke deposition and chlorine loss.

Multiple choice chemistry chemical kinetics dependence of reaction rate on concentration of reactants order of reactions factors influencing rate of a reaction

Which of the following statements is incorrect?

  1. A second order reaction must be a bimolecular elementary reaction

  2. A bimolecular elementary reaction must be a second order reaction

  3. Zero order reaction must be a complex reaction

  4. First order reaction may be complex or elementary reaction.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A bimolecular elementary reaction may or may not be a Second Order Reaction whereas a Second Order reaction must be a bimolecular elementary reaction.

Ex: Decomposition of ${N} _{2}O _{5}$ is a 1st Order Reaction though its a bimolecular reaction.

Multiple choice zoology endocrine system and chemical co-ordination mechanism of hormone action coordination in human beings- chemical control endocrine system in humans

A dehydration synthesis reaction is also known as

  1. A condensation reaction

  2. A hydrolysis reaction

  3. An isomeric reaction

  4. An energy-releasing reaction
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Dehydration means removal of water. It is a synthesis reaction where polymerization occurs in which the monomers are bound together which releases water as the end product or byproduct.

Hence, the correct answer is 'A condensation reaction'.