Which statement correctly describes ice and liquid water in a stoppered flask at 0°C at equilibrium?

• A. The temperature will gradually increase above 0°C.
• B. All of the ice will eventually melt.
• C. Only liquid water is present at equilibrium.
• D. The rates of melting and freezing are equal.

Answer: (D)

Verified step by step guidance

1. Understand the concept of phase equilibrium: At 0°C, ice and liquid water can coexist in a closed system when the rates of melting and freezing are equal.
2. Recognize that at equilibrium, the temperature remains constant because the energy added or removed is used for the phase change, not for changing temperature.
3. Recall that if the rates of melting and freezing are equal, the amount of ice and liquid water remains constant over time, so neither all ice melts nor only liquid water is present.
4. Note that if the temperature were to increase above 0°C, the ice would melt completely, which contradicts the equilibrium condition.
5. Conclude that the correct description is that the rates of melting and freezing are equal, maintaining a dynamic equilibrium between ice and liquid water at 0°C.