The metal iridium has an FCC crystal structure. If the angle of diffraction for
the {220} family of parallel planes occurs at 69.22? (first-order reflection) when
monochromatic x-radiation having a wavelength of 0.1542 nm is used,
compute
(a) the interplanar spacing for this set of planes, and
(b) the atomic radius for an iridium atom

Modern pennies are composed of zinc coated with copper. a student determines the mass of a penny to be 2.482 g and then makes several scratches in the copper coaling (to expose the underlying zinc). the student puts the scratched penny in hydrochloric acid, where the following reaction occurs between the zinc and the hcl (the copper remains undissolved): zn(s) + 2 hcl(aq) → h2(g) + zncl(aq)the student collects the hydrogen produced over water at 25 °c. the collected gas occupies a volume of 0.899 l at a total pressure of 79 j mmhg. calculate the percent zinc (by mass) in the penny. (assume that all the zn in the penny dissolves.)