What will be the boiling point of water at the top of a mountain?

Options

A. `100^(@)C`
B. `gt 100^(@)C`
C. `lt 100^(@)C`
D. Can't be determined

Explanation

To determine the boiling point of water at the top of a mountain, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Boiling Point Concept**: The boiling point of a liquid is the temperature at which its vapor pressure equals the surrounding atmospheric pressure. At sea level, this is 100 degrees Celsius for water.

2. **Consider Atmospheric Pressure Changes**: As we ascend to higher altitudes, such as the top of a mountain, the atmospheric pressure decreases. This lower pressure means that water will boil at a lower temperature than at sea level.

3. **Relate Pressure and Temperature**: According to the ideal gas law, for a constant volume of gas, the pressure (P) is directly proportional to the temperature (T). Thus, if the pressure decreases (as it does at higher altitudes), the temperature at which boiling occurs (T') will also decrease.

4. **Conclusion**: Since the pressure at the top of the mountain (P') is less than the atmospheric pressure at sea level (P), we can conclude that the boiling point of water at the top of the mountain (T') will be less than 100 degrees Celsius.

5. **Final Answer**: Therefore, the boiling point of water at the top of a mountain is less than 100 degrees Celsius.