For the following processes, state whether each of the thermodynamic quantities q, w, delta U, and delta H is greater than, equal to, or less than zero for the system described. Explain your answers briefly. Note: adiabatic means no heat flow, isothermal means constant temperature.

a. An ideal gas expands adiabatically against an external pressure of 1 bar.
b. An ideal gas expands isothermally against an external pressure of 1 bar.
c. An ideal gas expands adiabatically into a vacuum.
d. A liquid at its boiling point is converted reversibly into its vapor, at constant temperature and 1 bar pressure.
e. H2 gas and O2 gas react in a closed container at 25 degrees Celsius and the product water is brought back to 25 degrees Celsius.