Q$2.$ An unknown element has an atomic radius of $0\mathrm{.}1430$ nm and a density of $8\mathrm{.}57\frac{g}{c}{m}^3.$ Determine whether it has an FCC or a BCC crystal structure.

Q$3.$ Compute the number of kilograms of hydrogen that pass per hour through a $6-$mm thick sheet of palladium having an area of $0\mathrm{.}25m^2$ at $600C.$ Assume a diffusion coefficient of $1\mathrm{.}7{10}^8\frac{m^2}{s},$ that the respective hydrogen concentrations at the high$-$ and low$-$pressure sides of the plate are $2\mathrm{.}0$ and $0\mathrm{.}4k\frac{g}{m^2}$ of palladium, and that steady$-$state conditions have been attained.

Q$4.$ Determine the carburizing time necessary to achieve a carbon concentration of $0\mathrm{.}30wt\%$ at a position $4$ mm into an iron$-$carbon alloy that initially contains $0\mathrm{.}10wt\%C.$ The surface concentration is to be maintained at $0\mathrm{.}90wt\%C,$ and the treatment is to be conducted at $1100C.$ Use the diffusion data for $-$Fe in Table $5\mathrm{.}2.$

Q$5.$ A cylindrical specimen of an alloy having an elastic modulus of $207$ GPa and an original diameter of $10\mathrm{.}2$ mm experiences only elastic deformation when a tensile load of $8900$ N is applied. Compute the maximum length of the specimen before deformation if the maximum allowable elongation is $0\mathrm{.}25$ mm $.$