At the triple point of water there exists an equilibrium between

Options

A. ice and water
B. ice and vapours
C. ice, water and vapours
D. none of the above.

Explanation

To solve the question regarding the equilibrium at the triple point of water, let's break it down step by step.

### Step-by-Step Solution:

1. **Understanding the Triple Point**:
- The triple point of a substance is the specific temperature and pressure at which three phases of that substance coexist in thermodynamic equilibrium. For water, this occurs at a temperature of 0.01 °C and a pressure of 611.657 pascals.

2. **Identifying the Phases of Water**:
- Water exists in three distinct phases:
- **Solid**: This is ice.
- **Liquid**: This is liquid water.
- **Gas**: This is water vapor (steam).

3. **Equilibrium at the Triple Point**:
- At the triple point, all three phases (ice, liquid water, and water vapor) are present and in equilibrium. This means that the rate of conversion from one phase to another is equal.
- For example:
- Ice can melt to form liquid water.
- Liquid water can freeze to form ice.
- Liquid water can evaporate to form water vapor.
- Water vapor can condense to form liquid water.
- Ice can sublimate to form water vapor.
- Water vapor can deposit to form ice.

4. **Conclusion**:
- Therefore, at the triple point of water, there exists an equilibrium between solid (ice), liquid (water), and gas (water vapor).

### Final Answer:
At the triple point of water, there exists an equilibrium between solid (ice), liquid (water), and gas (water vapor).

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