Air at atmospheric pressure and 95°C flows at 20m/s over a flat plate of naphthalene 80cm long in the direction of flow and 60cm wide. Experimental measurements report the molar concentration of naphthalene in the air, CA, as a function of distance x from the plate as follows: Determine the molar flux of naphthalene from the plate surface under steady conditions.

Question no 2: Two large tanks are connected by a truncated conical duct as shown in figure. the diameter at z=0 is 6mm and the diameter at z=0.2m is 10mm. Gas compositions in the tanks are given in terms of mole percentages. The pressure and temperature throughout the system are 1 atm and 25 respectively and Dab = 3*10^-5

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Question 3: One way of measuring the diffusion coefficients of vapors is to place a small amount of liquid in a vertical capillary, generally known as the Stefan diffusion tube, and to blow a gas stream of known composition across the top as shown in figure. Show how one can estimate the diffusion coefficient by observing the decrease in the liquid gas interface as a function of time

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Question no 4: A liquid (A) droplet of radius R is suspended in a stagnant gas B as shown in Figure. We want to determine the rate of evaporation under steady conditions.

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Question no 5: A benzene droplet with a diameter of 8 mm is suspended by a wire in a laboratory. The temperature and pressure are maintained constant at 25 °C and 1 atm, respectively. Estimate the diffusion coefficient of benzene in air if the variation in the droplet diameter as a function of time is recorded as follows:

Solution:

The properties of Benzene

Question no 6: Gas A diffusion through a stagnant gas film to the surface of a nonporous cylindrical catalyst, where it undergoes the reaction . Gas B then diffusion from the catalyst surface and is swept away. Neglecting diffusion and reaction on the ends of the particle derive an equation for the molar flux of A if the reaction is very fast.

Solution