At a vacuum of 29 inches HG, what is the boiling point of water?

• A. 0°C
• B. 25°C
• C. 100°C
• D. -9.66°C

Answer: (B)

The boiling point of water decreases as atmospheric pressure is reduced. At a standard atmospheric pressure of 101.3 kPa (approximately 29.92 inches of mercury, or inHg), the boiling point of water is 100°C. However, as you create a vacuum and lower the pressure to 29 inches of mercury, which is below the standard atmospheric pressure, the boiling point of water drops.

At 29 inHg, the pressure corresponds to approximately 98.3 kPa. Under this reduced pressure, water will boil at about 25°C, which is significantly lower than the boiling point at sea level. The relationship between pressure and the boiling point of water is critical in various applications, particularly in refrigeration and in processes that involve vacuum conditions.

Therefore, boiling point at a vacuum of 29 inches of mercury is accurately associated with around 25°C, making this the correct answer. Understanding the principles of how pressure affects boiling points is essential for those involved in F-Gas and ODS regulations, as it relates to the handling and recovery of refrigerants in different pressure environments.