Skip to main content
Ch.11 - Liquids and Intermolecular Forces
Chapter 11, Problem 56c

Appendix B lists the vapor pressure of water at various external pressures. (c) A city at an altitude of 5000 ft above sea level has a barometric pressure of 633 torr. To what temperature would you have to heat water to boil it in this city?

Verified step by step guidance
1
Step 1: Understand that the boiling point of a liquid is the temperature at which its vapor pressure equals the external pressure. In this case, the external pressure is the barometric pressure at the city's altitude, which is 633 torr.
Step 2: Look up the temperature at which the vapor pressure of water is equal to 633 torr in Appendix B. This temperature is the boiling point of water at this altitude.
Step 3: If the exact value of 633 torr is not listed in the table, you may need to interpolate between two values to estimate the boiling point.
Step 4: Interpolation involves finding the two closest values to 633 torr in the table, and estimating the temperature based on these values. For example, if the vapor pressure of water is 600 torr at 90 degrees Celsius and 700 torr at 100 degrees Celsius, you could estimate that the boiling point at 633 torr is somewhere between 90 and 100 degrees Celsius.
Step 5: The exact temperature can be calculated by using the formula for linear interpolation: T = T1 + ((T2 - T1) / (P2 - P1)) * (P - P1), where T is the temperature you're trying to find, T1 and T2 are the temperatures at the two closest pressures, P1 and P2, and P is the pressure you're trying to find (633 torr in this case).

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
44s
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Vapor Pressure

Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid or solid form at a given temperature. It indicates how readily a substance will evaporate; higher vapor pressure means a substance will boil at a lower temperature. Understanding vapor pressure is crucial for determining boiling points under varying external pressures.
Recommended video:
Guided course
02:40
Raoult's Law and Vapor Pressure

Boiling Point

The boiling point of a liquid is the temperature at which its vapor pressure equals the external pressure surrounding the liquid. At higher altitudes, the atmospheric pressure is lower, which decreases the boiling point of water. This concept is essential for calculating the temperature needed to boil water in locations with different barometric pressures.
Recommended video:
Guided course
03:05
Boiling Point Elevation

Barometric Pressure

Barometric pressure, or atmospheric pressure, is the pressure exerted by the weight of the atmosphere above a given point. It varies with altitude; as altitude increases, barometric pressure decreases. This relationship is important for understanding how boiling points change in different geographical locations, such as cities at high elevations.
Recommended video:
Guided course
01:15
Pressure Units