Question 61. Consider loss of ethanol vapor by diffusion from a half-filled open test tube. At what point in the diffusion path will the contribution of the bulk flow term to the molar flux be maximum?

Question 62. For a component A of a mixture, concentration as a function of x is given:
Cᴀ=5e⁻¹⁰ˣ (x is in cm and Cᴀ in mol/liter)
Calculate the value of diffusion velocity (m/s) of the component A at the point x=0, if diffusivity of A in the mixture is 2.567*10⁻⁵m²/s.

Question 63. A reaction 3A+2B+C=1.5D+E occurs in a reactor at steady state. What will be the value of the flux ratio Nᴀ/Nᴅ

Question 64. A sheet of Fe 1.0 mm thick is exposed to an oxidizing gas on one side and a deoxidizing gas on the other at 725°C. After reaching steady state, the Fe membrane is exposed to room temperature, and the C concentrations at each side of the membrane are 0.012 and 0.075 wt%. Calculate the diffusion coefficient (m²/sec) if the diffusion flux is 1.4×10⁻⁸kg/m²-sec.

Question 65. At which condition molar flux with respect to a stationary observer and with respect to an observer moving with molar average velocity?

Question 66. Which among the following is the statement of the ‘Fick’s Law’?

Question 67. The mass transfer by convection can take place under how many conditions?

Question 68. The gas A diffuses through non-diffusing B from point 1 to point 2. The total pressure is 2atm and yᴀ₁=0.1 and yᴀ₂=0.Then the ratio (dPᴀ/dz)1/(dPᴀ/dz)2 is

Question 69. In industries titanium is hardened through diffusion of carbon. The concentration of carbon at 1mm into the surface of the titanium slab is 0.25kg/m³ and at 3mm the concentration is 0.68kg/m³. The rate at which the carbon is entering into its surface is 1.27*10⁻⁹kg/m².s. Calculate the value of diffusion coefficient of carbon.

Question 70. Lewis number is given by