Question

The energy for vacancy formation in BCC iron is 2.2 × 10^-19 J·mol^-1·K^-1. Calculate the fraction of lattice sites that would be vacant in 25 degree Celsius.

Answer 1

Ans;- Here Given,

temperature = 25⁰C = 25+273=298K

Energy for vacancy formation , E_v = 2.2x10^-19J/mol/K

Boltzmann constant , k = 1.38x10^-23 J/molK

Let f_v be the fraction of lattice sites ,

therefore

$f_{v}=exp(\frac{-E_{v}}{kT})$

      = exp[(-2.2x10^-19J/mol/K ) / 1.38x10^-23 J/molK x298K]

      =exp(-53.496)

      = 5.847x10^-24