@X@user.full_name@X@ @GMU: What is the fraction of A remaining after 83.913 minutes if the first order rate constant is 1.037e-4 s-1?

@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 0.1567. 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 would the pOH be after addition of 16.54 mL of 0.1000 M NaOH to 25.00 mL of 0.1000 HA (a weak acid, Ka = 9.23e-5)?

@X@user.full_name@X@ @GMU: Which product in the reaction below is a base (this one first in the answer) and which reactant is an acid?HS- + HSO-4 → H2S + SO24-

@X@user.full_name@X@ @GMU: Calculate the of 119.61 mL of a buffer initially consisting of 0.1875 M CH3(CH2)2CH2NH2 and 0.1069 M CH3(CH2)2CH2NH3Br after addition of 0.00344 mol of HCl. Assume that no volume change occurs after addition of the acid. The Kb of CH3(CH2)2CH2NH2 is 4.10e-4

@X@user.full_name@X@ @GMU: How much energy in kJ is released to form one mole of 116Cd from protons, electrons, and neutrons if the nucleus has a mass of 115.904755 amu? The masses of the proton, electron and neutron are 1.00728 amu, 0.000549 amu and 1.00867 amu, respectively.

@X@user.full_name@X@ @GMU: What is the fraction of A remaining after 62.466 minutes if the first order rate constant is 2.149e-4 s-1?

@X@user.full_name@X@ @GMU: What is the coefficient, b, in the reaction below, if Kc = 1.49e-6 and Kp = 2.50e-8 at 453.89°C?4A(s) + bB(g) → 3C(g)

@X@user.full_name@X@ @GMU: Determine the molality of a 8.983 wt % aqueous solution of NaF.

@X@user.full_name@X@ @GMU: To what temperature would you have to heat Zn(l) to cause its vapor pressure to become 284.7 mm Hg if its heat of vaporization and boiling point are 131.00 kJ/mol and 1180.2 K, respectively?