Although heat is a path function but heat absorbed by the system under certain specific conditions is independent of path. What are those conditions? Explain.

Explanation

The two conditions under which heat becomes independent of path are `:`
(i) When volume remains constant (ii) When pressure remains constant.
Explanation.(i) At constant volume . By first law of thermodynamics, `DeltaU= q+w` or`q=DeltaU`. But `w= - P DeltaV`. Hence, `q = DeltaU + P DeltaV`. But as volume remains constant,`DeltaV=0`.
`:. q_(v) = DeltaU`. But `DeltaV` is a state function. Hence, `q_(v)`is a state function.
(ii) At constant pressure. `q_(p) DeltaU +P DeltaV`. But `DeltaU +P DeltaV = DeltaH`
`:. q_(p) = DeltaH` . As `DeltaH ` is a state function, therefore, `q_(p)` is a state function.