Question

When a system is taken from state i to a state f along path iaf, Q = 50 J and W = -20 J. Along path fbi, Q = 36 J. If w = 13 J for the return path fi, Q for this path is

• A. 33 J
• B. 23 J
• C. -7 J
• D. -43 J

Answer 1

Answer: (D)

-43 J

given: we know the First law of thermodynamics

$\Delta U=Q-W$

Solution:

so on path iaf

$\Delta U=50-(-20)=70J$

along path fbi

$\Delta U=36-13=23J$

since for a cyclic path $\Delta U=0$ so here the change in internal energy needs to be dissipated / absorbed in the form of heat

$U2-U1=70-23=43J$

$Q=-43$ as heat is absorbed by the system

hence ,THE CORRECT OPTION IS D