Question

Which of the following are not state functions?
I.q + w
II.q
III.w
IV.H – TS
A.(I), (II) and (III)
B.(II) and (III)
C.(I) and (IV)
D.(II), (III) and (IV)

Answer 1

Hint: To answer the question, we need to know what are the quantities that are represented by the variables. And then the property can be categorized as a state function or not.

Complete answer:
- In thermodynamics, q is denoting the net heat transfer and w denotes the net work done. By q we mean the sum of all heat transferred into and out of the system. By w we mean the sum of all work done on or by the system. The sum of q and w is the internal energy.
- Though w and q are path functions, and not state functions. Both the quantities depend upon the path followed by the reaction or process.
- Internal energy is a state function, which does not depend upon the path but the initial and final point.
- Gibbs free energy is denoted by dG and is given by H – TS. H is the enthalpy, T is the absolute temperature of the system, and S is the entropy.
- Gibbs free energy is a state function. Its value decides whether the reaction will be spontaneous or nonspontaneous.

Therefore, the answer to the question is (B).

Note:
In thermodynamics, a state function or function of state or point function is a function defined for a system relating several state variables or state quantities that depends only on the current equilibrium state of the system.