One step in making para-aminobenzoic acid, paba, an ingredient in some suntan lotions,
involves replacing one of the hydrogen atoms in a toluene molecule with an - no2 group,
directly opposite the -ch3 group. calculate the percent yield if 550 g of toluene added to an
excess of nitric acid provides 305 g of the nitrotoluene product.

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.)