Chemqueries: State function and Path function

State function and Path function

State Function:

  • In thermodynamics, a state function, state quantity, or a function of state, is a property of a system that depends only on the initial and final state the system, not on the way in which the system acquired that state.
  • A state function describes the equilibrium state of  a system and thus also describes the types of system.
  • The cyclic integral involving a state function is always zero.
  • All the thermodynamics property satisfy the requirements of state function.
  • U = q + w         change in thermodynamic energy
    S = qrev/T            entropy
    H = U = PV         enthalpy
    G = H – TS          Gibb’s free energy
    A = U – TS          Helmholtz free energy
  • Internal energy, enthalpy, entropy are the example of state functions.

Path Function:

  • Path function depends on the path taken to reach that specific value, not on the initial and final state of that value.
  • Path function need multiple integral and limits of the integration in order to integrate.
  • It is based on how state of a system was established.
  • Work , heat, arc length are the example of path function.

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