Question

Thermodynamics assumes that matter is in its equilibrium state in order to make its calculations. Please, indicate whether or not the systems below may or may have not achieved an equilibrium state and explain your reason for your choice

1) A glass of water at room temperature and 1 atm held for 48 hr

2) A tray of water just placed in the icemaker section of the refrigerator

3) Corrosion of a metal in seawater

4) A closed teapot with boiling water at 212 oF and 1 atm

5) A piston-cylinder assembly containing a gas at 5 atm was suddenly released to 1 atm

Answer 1

1. A glass of water at room temperature and 1 atm held for 48 hr

Since the glass of water is at room temperature and pressure, it is in equilibrium with the surroundings.

There will be minor water loss because of evaporation. But on a macro scale it can be said to be in equilibrium state with the surroundings.

2. A tray of water just placed in the icemaker section of the refrigerator

Initially, tray water is at a higher temperature than ice maker section of the refrigerator. It is not in equilibrium state as it will exchange heat with the surroundings.

3. Corrosion of a metal in seawater

Corrosion of metal is a slow process. Practically it can be said to be in equilibrium state with the surroundings.

4. A closed teapot with boiling water at 212 ^oF and 1 atm

Assuming the teapot is thermally insulated, the system will be in equilibrium state with the surroundings.

5. A piston-cylinder assembly containing a gas at 5 atm was suddenly released to 1 atm

The gas will expand by pushing the piston of the assembly. The system is not in equilibrium state with the surroundings.