Of state. Contents and Concepts 1. Comparison of Gases, Liquids, and Solids Changes of State

A nswer Check The result should be less than 760 mmHg, because the vapor pressure is lower at a lower temperature. If you inadvertently dropped the minus sign before taking the antiln, you would have gotten a result larger than 760 mmHg. Also, if you had entered _H_vap in kilojoules, rather than joules, the result would be close to zero, which is not reasonable given that the water is at 85°C.

Exercise 11.2 Carbon disulfide, CS₂, has a normal boiling point of 46°C and a heat of vaporization of 26.8 kJ/mol. What is the vapor pressure of carbon disulfide at 35°C? See Problems 11.49 and 11.50.

Example 11.3 Calculating the Heat of Vaporization from Vapor Pressures

Calculate the heat of vaporization of diethyl ether (often called simply “ether”), C4H10O, from the following vapor pressures: 400 mmHg at 18°C and 760 mmHg at 35°C. (Each pressure value has three significant figures.)