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 chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

For an isolated system, the entropy:

  1. Either increases or remains constant

  2. Either decreases or remains constant

  3. Can never decrease

  4. Can never increase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The second law of thermodynamics states that the entropy of an isolated system never decreases, because isolated systems always evolve toward thermodynamic equilibrium, a state with maximum entropy.

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

Which of the following is a path function?

  1. Internal Energy

  2. Enthalpy

  3. Work

  4. All of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Path functions are properties or quantities whose values depend on the transition of a system from the initial state to the final state. The two most common path functions are heat and work

A physical quantity is said to be state function if its value depends only upon the state of the system and does not depend upon the path by which this state has been attained. E.g pressure, volume, temperature

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

Which of the following are state property?

  1. Internal energy (U)

  2. Volume (V)

  3. Heat (q)

  4. Enthalpy (H)
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
Explanation

Internal energy, volume and enthalpy are state properties. Their values are independent of  the path chosen to reach a particular state.
Heat is a path function. Its value depends on the path chosen to reach a particular state.

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

Which thermodynamic parameter is not a state function ?

  1. q at constant pressure

  2. q at constant volume

  3. W at adiabatic

  4. W at isothermal
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$W$ and $q$ are not state functions

$H$ and $U$ are state functions
$\Delta H = \Delta U + \Delta PV$

At constant pressure, $\Delta H = \Delta U + P\Delta V$   $\Delta P = 0$   $\Delta H = q _p$

At constant volume, $\Delta H = \Delta U + V \Delta P$   $\Delta V = 0$   $\Delta U = q _v$

So, the first two options are state function.
$\Delta U = q - W$     $(\because q = 0)$    $[ \therefore$ Adialentic process$]$

$\Delta U = -W$  (state function)
Work done in isotheromal process is not a state
function
$W = -q  (\because \Delta T = 0, q \neq 0)$
$\therefore$ option D is correct.

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

Identify the state functions from the following:

  1. heat

  2. work

  3. enthalpy

  4. none of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Enthalpy is a state function. Its value depends on the current state of the system and is independent of the path followed to reach that state. Mass, temperature, pressure and volume are also state functions. Heat and work are path functions.
Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

Among the following, the state functions are:

  1. Internal energy

  2. Irreversible expansion work

  3. Reversible expansion work

  4. Molar enthalpy
Reveal answer Fill a bubble to check yourself
A,D Correct answer
Explanation
State function is a quantity in thermodynamics, such as entropy or enthalpy, that has a unique value for each given state of a system. 
(or) 
A State Function is a thermodynamic quantity whose value depends only on the state at the moment, i. e., the temperature, pressure, volume, etc The value of a state function is independent of the history of the system's internal energy. Molar enthalpy and entropy are state quantities because they describe quantitatively an equilibrium state of a thermodynamic, irrespective of how the system arrived in that state.

Hence options A & D are correct.
Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

If a closed system has adiabatic boundaries, then atleast one boundary must be:

  1. permeable

  2. imaginary

  3. movable

  4. fixed
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Adiabatic boundaries mean there is no heat that is evolved or no heat exchange possible through it.

So, our system is closed that means matter cannot be exchanged but heat exchange can happen.

As here all the boundaries are adiabatic so to remain system closed at least one boundary should be movable to that heat exchange can take place.

Option C is correct.
Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

Which of the following statement is correct?

  1. Heat is thermodynamic property of system.

  2. Work is thermodynamic property of system.

  3. Work done by a conservative force is path function.

  4. Heat involved in chemical reaction is path independent physical quantity.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Heat and work are not thermodynamic properties and work done is independent of the object's path in a conservative force.

So, a,b,c are incorrect

A heat involved in the chemical reaction is path independent which is correct (from Hess's law)

Option D is correct.
Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

The enthalpy change for a reaction does not depend upon the:

  1. physical states of reactants and products

  2. use of different reactants for the same product

  3. nature of intermediate reaction steps

  4. difference in initial or final temperature of involved substances
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$\triangle H$ depends on :

  • Physical states of reactant and product.
  • Use of different reactants for the same product.
  • Difference in initial or final temperature of involved substances.
It is independent of nature of intermediate reaction steps because it is a path independent & is a state function.

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics
The change in enthalpy, $\Delta H$ accompanying a process depends on the path followed.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The change in enthalpy, $\Delta H$ accompanying a process does not depends on the path followed.
This is because the enthalpy of a reaction is a state function and its value depends on the inital and final states only.

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics
  Column I   Column II
a. Enthalpy p. Intrinsic property
b. Temperature q. Path function
c. Free energy r. Function $U, P, V$
d. Work s. State function
  1. $(a - r,s), (b - p,s), (c - r,s), (d - q)$
  2. $(a - r), (b - s), (c - r,s), (d - q, r)$
  3. $(a - r,s), (b - r), (c - p,s), (d - q)$
  4. $(a - q), (b - p,s), (c - s), (d - q, s)$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$(a\rightarrow r,s)$ Enthalpy is a state function and is a function of internal energy and pressure and volume.
$(b\rightarrow p,s)$ Temperature is independent of the bulk matter of the system and hence it is an intrinsic property but it is a state variable.
$(c\rightarrow r,s)$ Free energy is a state function as it depends on the state of the system as well as it depends on $H, T$ and $S$. It is also a function of $U, P$ and $V$.
$(d\rightarrow q)$ Work is a path function as the amount of work done depends upon path undertaken.

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

1 : $\Delta U$ is state function.

2: Heat and work are not state functions.

  1. $\text {only 1 is true}$
  2. $\text {only 2 is true}$
  3. $\text {both are true}$
  4. $\text {none of the above}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$\Delta U$ and heat are state functions. Their values depends only on the state of the system and are independent of the path followed. Work is a path function. Its value depends on the path followed .

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics
Internal energy change in a cyclic process is zero.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The given statement is true.
 Internal energy change in a cyclic process is zero.
Internal energy is a state function. It depends only upon the initial and final states of the system and is independent of the path followed. Hence, for a cyclic process, the initial and final value of the internal energy is same.