(a) For the solidification of iron, calculate the critical radius r* and the activation free energy ΔG* when the supercooling temperature is 295 °K. Values for the latent heat of fusion and surface free energy are –1.85 × 109 J/m3 and 0.204 J/m2 , respectively. (b) Now calculate the number of atoms found in a nucleus of critical size. Assume a lattice parameter of 0.292 nm for solid iron at its melting temperature.

If the atomic mass of an atom is 34 and the atom contains 13 protons, how many neutrons does the atom contain?

Express the following number in scientific notation. 0.026890 =

Tooth enamel consists mainly of the mineral calcium hydroxyapatite, ca_10(po_4)_6(oh)_2. trace elements in teeth of archaeological specimens provide anthropologist with clues about diet and diseases of ancient people. students at hamline university measured strontium in enamel from extracted wisdom teeth by atomic absorption spectroscopy. solutions with a constant total volume of 10.0 ml contained 0.726 mg of dissolved tooth enamel plus variable concentrations of added sr. added sr find the concentration of sr in the 10 ml sample solution in parts per billion = ng/ml. find the concentration of sr in tooth enamel in parts per million = mu g/g.