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STATE FUNCTION - PATH FUNCTION - THERMODYNAMICS MCQ
IIT JEE

1) Among the following the state function (s) is (are): 

(IIT JEE 2009)

1) Internal energy 

2) Reversible expansion work 

3) Irreversible expansion work 

4) Molar enthalpy

Logic:

* Thermodynamics definition of state function is: any property that depends only on the state of the system and not on the path taken to reach that state.

Solution:

The values of internal energy and Molar enthalpy depend only on the state and not on the path. 

However work is a path function. It is something that we measure while a system changes its position form one state to another state and can have any value depending on the path that is taken by the system to reach the final state.

Conclusion:

1 and 4 are correct options.

Related questions

2) Which of the following statements is false?

(IIT JEE 2001) 

1) Work is a state function.

2) Work appears at the boundary of the system.

3) Temperature is a state function.

4) Change in the state is completely defined when the initial and final states are specified.

Logic & solution: 

* Work appears only as change in the state at the boundary of the system. It is a path function. It can be defined as any quantity of energy that flows across the boundary between the system and surroundings which can be used to change the height of a mass in the surroundings.

Note: Think that how nonsense it is to say that a system at one point has this amount of work.

* Temperature is one of the variable that defines the state of a system.

Conclusion:

Statement given in option '1' is false.

Homework

1) What is the thermodynamic definition of heat?

2) State whether entropy is a state function or not?

 

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Author: Aditya vardhan Vutturi