A cubic particle of bromine (Br), 30 cm on a side, is placed in still air at -3C and 747 mm Hg pressure. Under these conditions the diffusion coefficient of bromine in air is 7.54x102 cms and the vapor pressure of bromine is 250 mm Hg. Over time, the Br particle reduces in size due to loss of mass through evaporation.

a) (2 point) Develop the equation that describes the evaporation of Br in air. b) (3 point) Determine the time required to completely evaporate the particle.