@X@user.full_name@X@ @GMU: NO2 at 354°C decomposes to form NO and O2 according to second order kinetics (see reaction below). The half-life for this reaction was measured to be 1.71e2 s when the initial concentration of NO2 was 3.25e-3 M. What is the rate constant for this reaction?2NO2(g) → 2NO(g) + O2(g)

@X@user.full_name@X@ @GMU: LiF has a face-centered cubic unit cell in which the F- anions occupy corners and face centers, while the cations fit into the hole between adjacent anions. What is the radius of Li+ if the ionic radius of F- is 136.0 pm and the density of LiF is 2.635 g/cm3?

@X@user.full_name@X@ @GMU: What is the standard free energy change for the ionization of H2S acid, if its Ka is 9.10e-8.

@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 0.1137. 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.

@X@user.full_name@X@ @GMU: What is the solubility in g/L of H2S at a partial pressure of 500.9 torr, if the solubility at a partial pressure of 364.0 torr is 1.616 g/L?

@X@user.full_name@X@ @GMU: What is the free energy change for the reaction below, if the reaction quotient, Q, at 25.0oC is equal to 4.66e-7?3C2H2(g) → C6H6(g) ΔGo = -498.180 kJ.

John Schreifels @GMU: What is the total entropy change at 25oC for the reaction below, if the standard entropies of reactants and products are So(C(gr)) = 5.74 J/mol*K, So (H2(g)) = 130.68 J/mol*K, and So (C7H12(g)) = 407.0900J/mol*K and the heat of formation of C7H12(g)) is 103.0600 kJ/mol.C7H12(g) → 7C(gr) + 6H2(g)

@X@user.full_name@X@ @GMU: NaF has a face-centered cubic unit cell in which the F- anions occupy corners and face centers, while the cations fit into the hole between adjacent anions. What is the radius of F- if the ionic radius of Na+ is 102.9 pm and the density of NaF is 2.558 g/cm3?

@X@user.full_name@X@ @GMU: What would the be after addition of 11.35 mL of 0.1000 M NaOH to 25.00 mL of 0.1000 HA (a weak acid, Ka = 1.06e-5)?

@X@user.full_name@X@ @GMU: What is the cell voltage for the following cell?2Cu+(aq) + Pb(s) → 2Cu(s) + Pb2+(aq) ΔGo = -125.430 kJ