During an isothermal process, 5.0 J of heat is removed from an ideal gas. What is the change in internal energy?
Zero... the internal energy for an ideal gas depends only upon the temperature. Therefore, an isothermal process has zero change in internal energy. (What does isothermal mean?)
Now if you asked what the work was, then it would be harder... The first law of thermodynamics is:
#DeltaU = q + w = 0#,
#q#is heat flow and #w = -PDeltaV#is work.
#q = -w#
and the work would just be:
#w = -q = -(-"5.0 J") = "5.0 J"#
since heat removed is negative with respect to the system (what is the system?). Did the gas get expanded or compressed?