Question

At room temperature, the equilibrium number of vacancies in pure aluminum is one vacancy every 107 atoms. Pure aluminum is heated to 650 oC where it has 1 vacancy every 1000 atoms at equilibrium. The crystal is then rapidly quenched to room temperature to prevent any vacancy from escaping or from reaching the equilibrium number of vacancies. After this rapid quenching, the density is accurately measured and found to be 2.698 g/cm3.

(i) Compare this density with the theoretical density for aluminum at room temperature.
(ii) What is the ratio of vacancies per 1000 atoms in the quenched crystal at room temperature? Given: Al is FCC with lattice constant of 0.4049 nm.

Answer 1