Question

What would be the boiling point of water if the air pressure over the liquid were reduced to 60 kPa

A) Approximately 60
B) Approximately 70°C
C) Approximately 80°C
D) Approximately 90°C

Answer 1

The boiling point of water at 60 kPa is just below approximately 90°C, correlating with a vapor pressure of water that is 68 kPa at around 90°C.

Step-by-step explanation:

The question asks about the boiling point of water under a reduced air pressure. Boiling occurs when a liquid's vapor pressure equals the external pressure. According to the provided information, water has a boiling point of approximately 80°C at 0.5 atm. Given that 1 atm is 101.3 kPa, a pressure of 60 kPa is lower than 0.5 atm. Referring to data presented in Figure 10.24, water's vapor pressure is 68 kPa at about 90°C. Hence, at 60 kPa, the boiling point of water would be lower than 90°C, but higher than the noted 80°C boiling point at a pressure of 0.5 atm.

Considering these factors, the correct answer to the student's question is D) Approximately 90°C. However, it's important to clarify that the actual boiling point at 60 kPa would be slightly below 90°C due to the specific pressure conditions.