Question

3.
Which of the following represents the First
law of thermodynamics?
(A) = AU - W (B) AH = q + W
(C) AU = AH + PAV
(D) AU = PAV​

Answer 1

Answer:

At constant temperature, ΔT=0

∴ΔU=nC

v

ΔT

∴ΔU=q+w=0

q=−w

When work done is zero, w=0

∴ΔU=q+w

∴ΔU=q

In gaseous system, w=PΔV

∴ΔU=q+w

∴ΔU=q+PΔV

When work is done by the system, w is negative.

∴ΔU=q−w