The activation energy for the diffusion of atomic species A in metal B is 124 kJ/mol. Calculate the diffusion coefficient at 802°C, given that the value of D at 1150°C is 7.7 × 10-12 m2/s.

Respuesta :

Answer:

[tex]D_{2} = 2.590\times 10^{-13}\,\frac{m^{2}}{s}[/tex]

Explanation:

The diffusion coefficient is computed by using this Arrhenius-type Model:

[tex]D = D_{o} \cdot e^{-\frac{E}{R_{u}\cdot T} }[/tex]

The following is constructed by dividing to two distinct diffusion coefficients:

[tex]\frac{D_{2}}{D_{1}} = \frac{e^{\frac{E}{R_{u}\cdot T_{1}} }}{e^{\frac{E}{R_{u}\cdot T_{2}}}}[/tex]

[tex]\frac{D_{2}}{D_{1}} = e^{\frac{E}{R_{u}}\cdot (\frac{1}{T_{1}}-\frac{1}{T_{2}} ) }[/tex]

Any diffusion coefficient at a different temperature can be found by using this formula:

[tex]D_{2} = D_{1}\cdot e^{\frac{E}{R_{u}}\cdot (\frac{1}{T_{1}}-\frac{1}{T_{2}} ) }[/tex]

[tex]D_{2} = (7.7\times 10^{-12}\,\frac{m^{2}}{s})\cdot e^{\frac{124000\,\frac{kJ}{kmol} }{8.314\frac{kPa\cdot m^{3}}{kmol\cdot K}}\cdot (\frac{1}{1423.15\,K}-\frac{1}{1075.15\,K} ) }[/tex]

[tex]D_{2} = 2.590\times 10^{-13}\,\frac{m^{2}}{s}[/tex]