21. Vanadium crystallizes in a body-centered cubic lattice, and the length of the edge of a unit cell is 305pm. What is the density of V? A) 5.961030g/cm3 B) 2.98106g/cm3 C) 2.98g/cm3 D) 5.96g/cm3 E) 11.9g/cm3 22. The triple point of iodine is at 0.12atm and 115C. Thus, liquid I2 A) Is more dense than I2 (s) B) Cannot exist above 115C. C) Is liquid at room temperature. D) Cannot have a vapor pressure less than 0.12atm. E) None of the above 23. A liquid boils when its A) Vapor pressure is exactly 1 atmosphere. B) Vapor pressure is equal to, or greater than, the external pressure pushing on it. C) Temperature is equal to 273K (standard temperature). D) Temperature is greater than room temperature. E) Temperature is greater than 298K and pressure greater than 1atm. 24. Which of the following substances is expected to have the highest molar heat of vaporization ( Hvap) ? A) Ar B) C6H6 C) He D) NH3 E) H2O 25. In which phase does the substance whose phase diagram is shown below exist at 40C and 0.5atm pressure? A) Gas B) Liquid C) Solid D) Supercritical fluid E) At critical conditions