Questions: Consider a situation in which a flask is half-filled with liquid water at room temperature. The partially filled flask is then sealed and given time to reach equilibrium. Which of the following statements are true? [Select all that apply.] Once the flask reaches equilibrium the rate at which water molecules move from the liquid to the gas phase is equal to the rate at which water molecules move, from the gas to the liquid phase. If given enough time, the water will evaporate completely. After the flask reaches equilibrium, there will no longer be any movement of individual water molecules from the gas phase into the liquid phase. After the flask reaches equilibrium, there will no longer be any movement of individual water molecules from the liquid phase into the gas phase. The rate of condensation decreases as the flask approaches equilibrium. The rate of condensation increases as the flask approaches equilibrium. The vapor pressure of the water is the total pressure in the flask after it reaches equilibrium. The vapor pressure of the water is the partial pressure of water (Pwater) in the flask after it reaches equilibrium.

Solution Steps

In a closed system, such as a sealed flask, equilibrium is reached when the rate of evaporation (liquid to gas) equals the rate of condensation (gas to liquid). This means that while individual molecules continue to move between phases, the overall amount of liquid and vapor remains constant.

1. Statement 1: "Once the flask reaches equilibrium the rate at which water molecules move from the liquid to the gas phase is equal to the rate at which water molecules move, from the gas to the liquid phase."

   • This statement is true because it describes the condition of dynamic equilibrium.

2. Statement 2: "If given enough time, the water will evaporate completely."

   • This statement is false. In a sealed system at equilibrium, the water will not evaporate completely because the rates of evaporation and condensation are equal.

3. Statement 3: "After the flask reaches equilibrium, there will no longer be any movement of individual water molecules from the gas phase into the liquid phase."

   • This statement is false. Even at equilibrium, individual molecules continue to move between phases; the net change is zero.

4. Statement 4: "After the flask reaches equilibrium, there will no longer be any movement of individual water molecules from the liquid phase into the gas phase."

   • This statement is false for the same reason as Statement 3.

5. Statement 5: "The rate of condensation decreases as the flask approaches equilibrium."

   • This statement is false. As the system approaches equilibrium, the rate of condensation increases until it equals the rate of evaporation.

6. Statement 6: "The rate of condensation increases as the flask approaches equilibrium."

   • This statement is true. As more molecules enter the vapor phase, the rate of condensation increases until equilibrium is reached.

7. Statement 7: "The vapor pressure of the water is the total pressure in the flask after it reaches equilibrium."

   • This statement is false. The vapor pressure is the partial pressure of the water vapor, not the total pressure in the flask.

8. Statement 8: "The vapor pressure of the water is the partial pressure of water ( \( \mathrm{P}_{\text {water }} \) ) in the flask after it reaches equilibrium."

   • This statement is true. The vapor pressure is defined as the partial pressure of the vapor in equilibrium with its liquid.

Final Answer