SOLUTION OF FICKS SECOND LAW EQUATION

In addition, the concentration gradient dC/dx for both concentration polarization and activation polarization can be determined from eqs. (4.38) and (4.40). Hence, for concentration polarization with C = Cx yields 

Substituting eq. (4.46) into (4.23) yields the Cottrell equation for the current density due to diffusion mass transfer [16,19] 

Figuie 4.9 Sdiematic nonlinear profiles of the electrical diai q. 

Exam 4.1 Consider the application of Pick s second law to solve an activation polarization problem. An electrochemical cell contains a bulk concentration and an electrode surface concentration of copper ions equal to 4x10 mol/cm and 10 nud/cm, respectively. If the dijfusivity of copper ions is 1.5x10 err fa, calculate a) the concentration of ions at 0.12 mm from the electrode surface after 10 minutes and b) the time for a concentration of 10 mol/cm of ions at 0.10 mm from the electrode surface. 

Example 4.2 Assume that two columns of ionic solutions are connected by a barrier, such as a diaphragm. If the barrier is suddenly removed at time = 0, free diffusion takes place. Derive an expression for a) the concentration Cx at x = o and b) the molar fluxjj. in the x-direction at x = o and c)Cx Co V5. xjy/ADi. Determinee CxICo from the plot at x = 0, and d) plot the molar flux Jx VS. time atx = 0. Given data D = 10 crr js, C = 10- molfcn.  

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