On a cold winter day when the temperature is -20°C, what is the amount of heat needed to warm to 37°C (internal body temperature) the 0.50 L of air exchanged with each breath? Assume that the specific heat capacity of air is 1020 J (kg. Cº) and that 1.0 L of air has a mass of 1.3 g.

Carbon is allowed to diffuse through a steel plate 15 mm thick. the concentrations of carbon at the two faces are 0.65 and 0.30 kg c/m^3 fe, which are maintained constant. if the preexponential and activation energy are 6.2 x 10-7 m2 /s and 80,000 j/mol, respectively, compute the temperature at which the diffusion flux is 1.43 x 10^-9 kg/m^2 -s.