Tag: basics of thermodynamics

Questions Related to basics of thermodynamics

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

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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

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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

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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. $\text {none of the above}$

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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

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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

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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

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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.

Choose the correct answer. 

A thermodynamic state function is a quantity : 

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

  1. used to determine heat chages

  2. whose value is independent of path

  3. used to determine pressure volume work

  4. whose value depends on temperature only

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Correct Option: B
Explanation:

A thermodynamic state function is a quantity whose value is independent of path. Thus, enthalpy is a state function.
Its value depends on iniital and final states and is independatn of path followed.

Among the following, the state function are

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

  1. internal energy

  2. molar enthalpy

  3. reversible expansion work

  4. irreversible expansion work

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Correct Option: A,B
Explanation:

State functions are path Independent

For example: $E$ (Internal energy), Molar enthalpy, entropy etc.

Why are state functions important in chemistry?

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

  1. They appear a lot in thermochemistry and thermodynamics

  2. Many equations include properties that are state functions

  3. We only need to know the final and initial states

  4. They simplify our calculations

  5. All answers are correct

Show answer
Correct Option: C
Explanation:
State functions help us simplify our calculations and see the change in value between the final and starting position, also known as a state change. Mass, pressure, density, energy, temperature, volume, enthalpy, entropy, Gibbs free energy and chemical composition are all examples of state functions in thermochemistry
In simple words, the state functions are important in chemistry as we only need to know the final and initial states.

Hence, the correct option is $C$