Key relationships from diagram:

• Isothermal ideal gas: $\Delta U = 0$, $\Delta H = 0$
• Adiabatic: $q = 0$, $\Delta U = w = nC_v\Delta T$
• Isochoric: $w = 0$, $\Delta U = q_v$
• Isobaric: $q = \Delta H = nC_p\Delta T$