Answer to Question #133938 in Molecular Physics | Thermodynamics for kgokane sekgoka

Question

Standard room temperature is 21° C and the boiling point of water in Pretoria is 99° C. Explain why the boiling point it is not exactly 100° C?

Answer 1

The boiling point refers to the temperature at which the vapor pressure of a liquid becomes equal to the ambient pressure. Therefore, the lower the ambient pressure, the lower the boiling point. The boiling point of 100^oC for water is measured at the pressure of 1 atm (760 mmHg), which is typically observed at the sea level. Pretoria is located significantly above the sea level, hence the ambient pressure in the city is lower compared to the sea level. That is why the boiling point of water is also lower than 100^oC.