Agas is inside a cylinder fitted with a piston. the gas and its surroundings are both at 20 ∘c and the gas is compressed as the piston moves and decreases the cylinder volume. the compression takes place slowly enough to allow the gas temperature to stay at 20 ∘c and the work done on the gas by the compression is 2.4 × 103 j.

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.)