Factors that Influence Diffusion III Carbon is allowed to diffuse through a steel plate 13-mm thick. The concentrations of carbon at the two faces are 0.702 and 0.110 kg of carbon per m³ of iron, which are maintained constant. If the preexponential and activation energy are 6.5 x 10^-⁷ m²/s and 82 kJ/mol, respectively, calculate the temperature (in K) at which the diffusion flux is 3.2 x 10-⁹ kg/(m²-s).

Respuesta :

Answer:

[tex]T=899.849K=626.7\°c[/tex]

Explanation:

We need to use Fick's Law to resolve this problem.

We know for this Law that:

[tex]J=-D\frac{\Delta c}{\Delta x}[/tex]

And we know as well that the diffusivity coefficient can be expressed as follows,

[tex]D=D_0 e^{-\frac{Ed}{RT}}[/tex]

Where J is the flux of atoms, D is the diffusivity, R is the gas constant, Ed is the activation energy and \frac{\Delta c}{\Delta x} is the concentration of gradient.

To calculate the temperature we need to remplace the equation of diffusivity coefficient in the Fick's law equation.

[tex]J=-D\frac{\Delta c}{\Delta x} = -D_0 e^{-E_d/RT}\frac{\Delta c}{\Delta x}[/tex]

Rearrange the equation to get the value of temperature

[tex]ln(\frac{J\Delta x}{D_0 \Delta c})=(-\frac{E_d}{RT})[/tex]

[tex]T=-\frac{E_d}{Rln(\frac{J\Delta x}{D_0 \Delta c})}[/tex]

We have all the values,

[tex]\Delta x= 10*10^{-3}m\\\Delta c= 0.85-0.40 =0.45kg.c.cm^{-1}[/tex]

[tex]Ed=-80000Jmol^{-1}K^{-1}\\R=8.31Jmol^{-1}K^{-1}\\J=6.3*10^{-10}kg.m^{-2}\\D_0 = 6.2*10^{-7}m^2s^{-1}[/tex]

So  substituting,

[tex]T=\frac{-80000}{8.31*ln(\frac{(6.3*10^{-10})(10*10^{-3})}{6.2*19^{-7}*0.45})}[/tex]

[tex]T=899.849K=626.7\°c[/tex]

Q&A Education