Tag: introduction to thermodynamics

Questions Related to introduction to thermodynamics

Which of the following is path function? 


A. $W$
B. $Q$
C. $\Delta G$
D. $\Delta H$

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

  1. A and D

  2. A and B

  3. A, B and D

  4. A, C and D

Show answer
Correct Option: B

Identify the state functions from the following:

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

  1. heat

  2. work

  3. enthalpy

  4. none of the above

Show answer
Correct Option: C
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.

Among the following, the state functions are:

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

  1. Internal energy

  2. Irreversible expansion work

  3. Reversible expansion work

  4. Molar enthalpy

Show answer
Correct Option: A,D
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.

A closed vessel contains equal number of nitrogen and oxygen molecules at a pressure of P mm. If nitrogen is removed from the system, then the pressure will be?

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

  1. P

  2. $2P$

  3. $P/2$

  4. $P^2$

Show answer
Correct Option: C
Explanation:

$\dfrac{p _1}{n _1}=\dfrac{p _2}{n _2}$ (As molecules of $N _2=$ molecules $O _2$)
($\therefore$ Moles $N _2=$moles $O _2$)
As $N _2$ molecules removed$=$ moles become half
$\dfrac{p _1}{1}=\dfrac{p _2}{1/2}$
$p=\dfrac{1}{2}p _1$
$\therefore$ Pressure reduced to half
$\therefore$ Answer is option C.

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

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

  1. permeable

  2. imaginary

  3. movable

  4. fixed

Show answer
Correct Option: C
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.

Which of the following statement is correct?

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

  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.

Show answer
Correct Option: D
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.

The open system(s) is/are which

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

  1. can exchange matter with the surroundings

  2. can exchange energy with the surroundings

  3. can exchange both matter and energy with the surroundings

  4. cannot exchange either matter or energy with the surroundings

Show answer
Correct Option: A,B,C
Explanation:

Types of system : 
(i)Closed system : A system which can exchange only energy with surrounding. 
(ii)Open system : A system which can exchange both energy and matter with surrounding. 
(iii)Isolated system : A system which cannot exchange matter or energy with surrounding.

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

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

  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

Show answer
Correct Option: C
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.

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

  1. True

  2. False

Show answer
Correct Option: B
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.

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

  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. $(a - q), (b - p,s), (c - s), (d - q, s)$

Show answer
Correct Option: A
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.