Which of the following processes involves zero work done?

The internal energy change when a system goes from state $A$ to $B$ is $40 \, kJ/mol$. If the system goes from $A$ to $B$ by a reversible path and returns to state $A$ by an irreversible path,what would be the net change in internal energy?

In which of the following reactions is $\Delta E = \Delta H$?

Which of the following processes exhibits $\Delta U = 0$?

Three moles of an ideal gas expanded spontaneously into vacuum. The work done will be .............. $Joules$.

In an exothermic reaction,the reactants: