@X@user.full_name@X@ @GMU: What is the temperature at which…

@X@user.full_name@X@ @GMU: What is the temperature at which the reaction below becomes spontaneous, if the standard entropies of reactants and products at 25oC are So (C(gr)) = 5.74 J/mol*K, So(H2(g)) = 130.68 J/mol*K, and So (C9H16(g)) = 484.8200J/mol*K and the heat of formation of C9H16(g)) is 61.8300 kJ/mol?C9H16(g) → 9C(gr) + 8H2(g)

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

@X@user.full_name@X@ @GMU: RbBr has a face-centered cubic unit cell in which the Br- anions occupy corners and face centers, while the cations fit into the hole between adjacent anions. What is the radius of Rb+ if the ionic radius of Br- is 195.0 pm and the density of RbBr is 3.350 g/cm3?

@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 0.1950. 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.