A spherical ball of solid, nonporous naphthalene, a "mothball," is suspended in still air. The naphthalene ball slowly sublimes, releasing the naphthalene vapor into the surrounding air by the molecular diffusion-limited process. Estimate the time required to reduce the diameter from 2.0 to 0.50 cm when the surrounding air is at 347 K and 1.0 atm. Naphthalene has a molecular weight of 128 g/mol, a solid density of 1.145 g/cm3, and diffusivity in the air of 8:19 10␣6 m2=s, and exerts a vapor pressure of 5.0 Torr (666 Pa) at 347 K.