@X@user.full_name@X@ @GMU: LiCl has a face-centered cubic un…

@X@user.full_name@X@ @GMU: LiCl has a face-centered cubic unit cell in which the Cl- anions occupy corners and face centers, while the cations fit into the hole between adjacent anions. What is its density if the ionic radii of Li+, Cl- ions are 76.22 pm and 181.0 pm, respectively?

@X@user.full_name@X@ @GMU: Uranium -238 decays in a series o…

@X@user.full_name@X@ @GMU: Uranium -238 decays in a series of steps to Pb-206. When the material is very old, one can treat the kinetics as a decay directly to Pb and the ratio of these two can be treated as a measure of the age of a rock. A rock containing 238U and 206Pb was examined to determine its approximate age. The molar ratio of 206Pb to 238U was 0.1852. Assuming no lead was originally present and that all lead formed remained in the rock, what is the age of the rock (in years)? The half-life of 238U is 4.50e9 yr.