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# Exchange Current Density of Metal Ions

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The following data were obtained for the reduction of metal ions A+ to metal A in a stirred solution at a 0.1 cm^2 electrode; the solution contained 0.01M A+.

n(mV) -100 -120,-150, -180, -220, -280, -370, -500, -600
i(uA) -45.9, -62.6, -100, -170, -300, -510, -770, -965, -965

Calculate the exchange current density jo[uA/cm^2], the symmetry factor, Beta, and the thickness of the diffusion layer, delta[cm], knowing the diffusion coefficient, D(A+)=1.3 x 10^-5 cm^2/s. What will be the surface concentration of A+[M], c^s A+, at overpotential of -280 mV?

https://brainmass.com/chemistry/oxidation-reduction-and-electrochemistry/exchange-current-density-of-metal-ions-70804

#### Solution Summary

This solution contains step-by-step calculations to determine the exchange current density, symmetry factor, beta, thickness of diffusion, delta and surface concentration. In addition, a Tafel plot is included to illustrate the trends in the data.

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## Rate Limiting Steps in Metal Oxide Epitaxy

On the bottom right-hand side of the third page of the pdf attached (page 2 of the article), the author states:

"Metal deposition rates are easily converted into the oxide growth rate under the assumption that the metal arrival rates are the rate limiting steps, which is true for growth under oxygen- rich conditions."

I am having trouble understanding this, so please answer the following questions to clarify it for me.

(a) What is meant by metal arrival rates being "rate limiting steps?" (Does this refer to oxidation?)

(b) Why is this true? (Why are metal arrival rates rate limiting steps?)

(c) What exactly is meant by an "oxygen-rich environment?" I haven't seen a technical definition of an "oxygen-rich environment" anywhere in the literature.

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