Anyone help with this percent yield question?

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.)

Abaker touches a pie right after taking it out of the oven. which statement best explains why the pie feels hot?

Based on the formulas, select the compounds below that are covalent: kbr sif4 al2o3 co2 naco3 s7o2 pcl3 fe3n2 h2o s2f10