Groupwork 7 Reversibility

Name: ______________________________

Section: _____________________________

Student ID#:__________________________

Work in groups on these problems. You should try to answer the questions without referring to your textbook. If you get stuck, try asking another group for help.

An important concept in thermodynamics is that of reversibility.  This groupwork focuses on this topic.

Some key equations:

$$dS=\frac{\sigma q}{T}$$Reversible process:  $$dS=\frac{\sigma q_{rev}}{T}$$         Reversible constant pressure:  $$\Delta S_{P,rev}=\frac{\Delta H_{rev}}{T}$$   Total entropy change:  $$\Delta S_{total}=\Delta S_{system}+\Delta {surroundings} \geq 0$$

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Consider the following processes.  Which are reversible?  Which are irreversible?  Discuss and explain your responses. In each case, what is the system and what is the surroundings. If you can, describe how you would determine the entropy change of the system and the surroundings.  Is $$\Delta S_{total}$$ for each process greater than or equal to zero?

1. Compression of a gas from 1 bar to 2 bar in infinitesimal steps while keeping the heat constant in the system?

1. Expansion of a gas against constant pressure from 1 liter to 2 liters.

1. An ice cube melting in a glass of room temperature water.

1. Water vapor forming above the surface of water when the water and the air are both at 100 ˚C (at sea level).

1. Expansion of a gas at constant temperature from 1 liter to 2 liters in infinitesimal steps.

1. Vaporization of water at its boiling point.

1. Vaporization of water above its boiling point.