3. a 2.5 mm thick steel pipe (diameter 25 cm) transports nitrogen gas at a temperature of 500°c. in any 10 cm section of the pipe, nitrogen atoms are "lost" into the external environment at a rate of 7.5 x 108 atoms/s. if the nitrogen concentration at the exterior pipe surface is 1.5 x 1012 atoms/cm3, find the nitrogen concentration at the interior pipe surface. the diffusion constants for nascent nitrogen in steel are do = 0.003 cm2/s, q = 76.1 kj/mol and r = 8.314 j/k·mol.