@X@user.full_name@X@ @GMU: When 2.931 g of urea was dissolve…

@X@user.full_name@X@ @GMU: When 2.931 g of urea was dissolved in 100.6 g of benzene, the freezing point was 276.2 K. What is the formula mass of this compound? The freezing point depression constant for benzene is 5.12 (°C*kg)/mol. The melting point and boiling points are 5.50°C and 80.10°C, respectively.

@X@user.full_name@X@ @GMU: When 10.52 g of aspirin was disso…

@X@user.full_name@X@ @GMU: When 10.52 g of aspirin was dissolved in 104.9 g of benzene, the freezing point was 275.7 K. What is the formula mass of this compound? The freezing point depression constant for benzene is 5.12 (°C*kg)/mol. The melting point and boiling points are 5.50°C and 80.10°C, 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 0.2212. 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.