Ice ⇌ Water
In which direction equilibrium will shift forward or backward on increasing pressure at constant temperature?

Answer

To determine the direction in which the equilibrium between ice and water will shift when pressure is increased at constant temperature, we can follow these steps:

### Step 1: Understand the equilibrium reaction
The equilibrium reaction we are considering is:
\[ \text{Ice (s)} \rightleftharpoons \text{Water (l)} \]

### Step 2: Analyze the states of matter
In this reaction, ice is a solid (s) and water is a liquid (l). We need to consider the volume associated with each state:
- Ice (solid) has a lower density and occupies more volume than water (liquid).

### Step 3: Apply Le Chatelier's Principle
According to Le Chatelier's Principle, if a system at equilibrium is subjected to a change in pressure, the equilibrium will shift in the direction that counteracts that change.

### Step 4: Consider the effect of increasing pressure
When pressure is increased, the system will shift to the side that occupies less volume to counteract the increase in pressure.

### Step 5: Determine the volume change
Since ice occupies more volume than water, increasing the pressure will favor the formation of water (the liquid state) because it has a smaller volume.

### Conclusion
Thus, when pressure is increased at constant temperature, the equilibrium will shift backward (to the left) towards the formation of ice.

### Summary of the solution:
1. The equilibrium reaction is Ice (s) ⇌ Water (l).
2. Ice has a larger volume than water.
3. Increasing pressure will shift the equilibrium towards the side with less volume.
4. Therefore, the equilibrium will shift backward (toward ice) when pressure is increased.