Question

In a process, 701 J of heat is absorbed by a system and 394 J of work is done by the system. What is the change in internal energy for the process?

Answer 1

According to the first law of thermodynamics,
$∆U = q + W$ ......... (i)
Where,
$∆U$ = change in internal energy for a process
$q$ = heat
$W$ = work
Given,
$q$ = $+ 701\ J$ (Since heat is absorbed)
$W$ = $–394\ J$ (Since work is done by the system)
Substituting the values in expression (i), we get
$∆U$ = $701\ J + (–394\ J)$
$∆U$ = $307\ J$

Hence, the change in internal energy for the given process is $307\ J$.