Consider the following four cases
i. A c

Question

Consider the following four cases
i. A chemical process in which heat is absorbed.
ii. A change in which q = 30 J, w = 44 J.
iii A process in which a system does work on its surroundings with no change in q.
iv. A process in which work is done on a system and an equal amount of heat is withdrawn.
In how many of these cases does the internal energy of the system decrease?
O 0
O 1
O 2
O 3
O 4

Kunduz · Accepted Answer

This is a first law of thermodynamics question: Q-W=AU Q = heat in, W = work out, U = internal energy Let us look at each process in turn: 1. A chemical process in which heat is absorbed. Q>0. If no work is done, AU > 0, so U increases. 2. A change in which q=30 J, w=44 J. (I am assuming you are using the convention where work out is positive.) Q-W=(30-44) J = -14 J = AU In this case, U decreases. 3. A process in which a system does work on its surroundings with no change in q. Q-W=0-W=-W=AU, so by the first law, U decreases. 4. A process in which work is done on a system and an equal amount of heat is withdrawn. Q-W=AU, with W<0, Q<0, and |W| = |Q1 -|Q|+|W|=0 hence U = O no decrease energy option c is correct

Consider the following four cases i. A chemical process in which heat is absorbed. ii. A change in which q = 30 J, w = 44 J. iii A process in which a system does work on its surroundings with no chang