Tag: chemical thermodynamics

Questions Related to chemical thermodynamics

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.

State whether the given statement is true or false:

Enthalpy change is dependent on temperature and on the path adopted.
chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

State variables : To define a thermodynamics states of a system, we have to specify the values of certain mesurable quantities. These are called thermodynamic  variable or state variable. A system can be completely defined by four variables namely pressure, temperature, volume and composition. A system is said to be in a certain definite state when all of its properties have definite value.. Between two fixed state the change in the value of state function is same irrespective of the path connection two states.

Example : T, V, P and U (internal energy), H (enthalpy) are state variables.
As enthalpy is state variable so it will depend upon temperature only, not on path.

A system which cannot exchange matter and energy with the surroundings called isolated.

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

  1. True

  2. False

  3. Ambiguous

  4. None of these

Show answer
Correct Option: A
Explanation:

A system which  cannot exchange matter and energy with the surroundings called isolated system.
A liquid in a sealed thermos flask and ice in a thermos flask are examples of isolated systems.

Which one of the following quantity is dependent on path?

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

  1. Molar internal energy

  2. Volume

  3. W

  4. Q+W

Show answer
Correct Option: C
Explanation:

Work is a path dependent quantity. It is known as a path function.

1 : $\Delta U$ is state function.

2: Heat and work are not state functions.

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

  1. $\text {only 1 is true}$

  2. $\text {only 2 is true}$

  3. $\text {both are true}$

  4. $\text {none of the above}$

Show answer
Correct Option: C
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 .

Like $U$ and $H, S$ is also a state function.

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

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

As we know,

Between two fixed state the change in the value of state function is same irrespective of the path connection two states.  Differential of a state function  integerated over a cyclic path returns zero. In other words summation of change in state function in a cyclic process is equal to zero. Example : T, V, P and U (internal energy), H (enthalpy) are state variables.

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

  1. True

  2. False

Show answer
Correct Option: A
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.

Which of the following is a path function?

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

  1. internal energy

  2. enthalpy

  3. work

  4. entropy

Show answer
Correct Option: C
Explanation:

Path functions are properties or quantities whose values depends on the transaction of a system from the initial state to the final state. The two most common path functions are heat and work.