PLEASE EXPLAIN CLEARLY

a. The diffusivity of the binary gas system cyclohexane-nitrogen is to be determined from the measured rate of evaporation of liquid cyclohexane, which partially fills a vertical, narrow glass tube. A steady stream of pure nitrogen is blown across the top of the tube, which has an internal diameter of 1 cm. The system is at 15C, the total pressure is 1 atm, and the liquid level is located 10 cm below the top of the tube at the start of the experiment. If the drop in level is 0.21 cm after 20 h of continuous operation, calculate the diffusivity DAB (in cm2 /s) under these conditions. The density and vapor pressure of cyclohexane at 15C are 0.779 g/cm3 and 0.082 atm, respectively. Molecular weight of cyclohexane is 84.16.

b. Calculate the molar evaporation flux of cyclohexane, NA in g mol/(cm2 . s), at steady state.