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

The maximum theoretical work obtainable, when a system interacts to equilibrium with a reference environment, is called

  1. Entropy

  2. Enthalpy

  3. Exergy

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

Entropy: Degree of randomness in the system. Enthalpy (H ) = U + PV U = Internal energy PV = Displacement work So enthalpy is the sum of internal energy and displacement work. Exergy or Available Energy: The maximum portion of energy which could be converted into useful work by ideal process and it reduces the system to dead state. Dead state: It is a state in equilibrium with the earth and its atmosphere.

Multiple choice

The following table of properties was printed out for saturated liquid and saturated vapour of ammonia. The titles for only the first two columns are available. All that we know is that the other columns (columns 3 to 8) contain data on specific properties, namely, internal energy (kJ/kg), enthalpy (kJ/kg) and entropy (kJ/kg.K).

             
T(0C)
P(kPa)

||||||| | -20 | 190.2 | 88.76 | 0.3657 | 89.05 | 5.6155 | 1299.5 | 1418.0 | | 0 | 429.6 | 179.69 | 0.7114 | 180.36 | 5.3309 | 1318.0 | 1442.2 | | 20 | 857.5 | 272.89 | 1.0408 | 274.30 | 5.0860 | 1332.2 | 1460.2 | | 40 | 1554.9 | 368.74 | 1.3574 | 371.43 | 4.8662 | 1341.0 | 1470.2 |

When saturated liquid at 40°C is throttled to -20°C, the quality at exit will be

  1. 0.189

  2. 0.212

  3. 0.231

  4. 0.788
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

constant wall temperature conditions and for turbulent flow,Nu=0.023$Re^{0.8}$$Pr^{0.33}$

Multiple choice

Directions: The following question has four choices out of which ONLY ONE is correct.

Find the wrong statement regarding the factors affecting the chemical reactions.

  1. The rate of photochemical reaction is independent of radiations.

  2. A catalyst increases the rate of a chemical reaction at a particular temperature only.

  3. The rate of chemical reaction is directly proportional to the concentration of the reactants.

  4. The rate of chemical reaction depends on number of collisions.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The rate of photochemical reaction increases by absorption of photons of certain radiations.

Multiple choice

Which of the following statements is incorrect regarding the postulates of collision theory of chemical reactions?

  1. The colliding molecules should possess threshold energy to yield products.

  2. Activation energy = [Threshold energy - energy of the molecules at normal state]

  3. The molecules acquiring the threshold energy are called activated molecules.

  4. All collisions between the reacting molecules can form the products.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Collisions taking place between activated molecules are called activated collisions. Only the activated collisions can lead to the formation of the products in the chemical reaction.

Multiple choice

A chemical reaction at equilibrium is exothermic in the forward direction and endothermic in backward direction. What is the effect of increase of temperature on it?

  1. The equilibrium will shift in the backward direction so as to consume the heat evolved.

  2. The equilibrium shifts in the forward direction so as to liberate more heat.

  3. Equilibrium is not affected by change of temperature.

  4. It cannot be predicted.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

According to Le Chateliers principle, the increase of temperature should shift the reaction in the direction of absorbing the heat, i.e. the backward direction. So, the equilibrium will shift in the backward direction to consume the heat evolved.

Multiple choice

In a certain chemical reaction, the number of moles of products are lesser than the number of reactants. What will happen if the pressure on the system is increased?

  1. Equilibrium will shift in the backward direction forming more reactants so as to minimise the extent of formation of products.

  2. Equilibrium will shift toward in the direction of the formation of products so as to minimise the applied pressure.

  3. Equilibrium remains unaffected by increasing the pressure.

  4. It cannot be predicted.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

As per the Le Chatelier's principle, the increase of external pressure shifts the equilibrium in a direction which lowers the pressure, i.e. the equilibrium shifts in a direction that forms lesser number of moles of the gas.

Multiple choice

What information cannot be derived from a chemical equation?

  1. Relative molecular masses of different substances

  2. Law of indestructibility of matter

  3. Concentration of reactants and products

  4. Quantity of reactants taking part and products formed
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Chemical reaction does not tell about Concentration of reactants and products. It is the limitation of a chemical equation.