Question

A chemical process in which heat is absorbed.

A change in which q=30 J, w=44 J.
A process in which a system does work on its surroundings with no change in q.
A process in which work is done on a system and an equal amount of heat is withdrawn.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? (0,1,2,3,4)

Answer 1

Number of cases where internal energy of system decreases = 1

Step-by-step explanation:

According to first law of thermodynamics-

`\Delta U=q+w`

where,
`\Delta U`, q and w represents change in internal energy, heat exchanged and work done respectively.

• When heat is absorbed (q > 0),
  `\Delta U` will also increase.

• When q = 30 J and w = 44 J,
  `\Delta U` = (30+44) J = 74 J (positive). So, internal energy of system increases.

• When q = 0 and system does work on its surroundings (w < 0),
  `\Delta U` < 0 (negative). So, internal energy of system decreases.

• When work id done on system (w > 0) and heat is withdrawn (q < 0) by an equal amount (w = -q),
  `\Delta U=0`. So, internal energy does not change.

So, number of cases where internal energy of system decreases = 1