Q37Short answer
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.
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At constant volume By first law of thermodynamics: q = ∆U + (–w) (–w) = p∆V ∴ q = ∆U + p∆V ∆V = 0, since volume is constant. ∴ qV = ∆U + 0 ⇒ qV = ∆U = change in internal energy At constant pressure qp = ∆U + p∆V But, ∆U + p∆V = ∆H ∴ qp = ∆H = change in enthalpy. So, at a constant volume and at constant pressure heat change is a state function because it is equal to change in internal energy and change in enthalpy respectively which are state functions.