Place these refrigerators in order from the least power to the most power. Refrigerator A uses 1000 J over 60 seconds.
Refrigerator B uses 1500 J over 40 seconds.
Refrigerator C uses 2400 J over 180 seconds

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

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.)

How do you know when a chemical reaction has occurred