When you combine the intermediate chemical equations, which substance do you cancel out?

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.)

One nanometer is equal to how many meters?

Plz a person walks 1 mile every day for exercise, leaving her front porch at 9 am and returning to her front porch at 9: 25 am what was the total displacement of her daily walk a. 1 mile b. 0 c. 25 min d. none of the above