Question

The following describes the reaction between a copper penny and nitric acid in an open beaker:
Cu (s) + 4 HNO3 (aq) --> Cu(NO3)2 (aq) +2 H2O (l) + 2 NO2 (g)
The mass of the beaker and contents was monitored until the reaction ended. The results: (224.6g, 0s) and (215.8g, 118.6s)
What chemical is represented by the change in mass? Explain why it cannot be the mass change of copper.

Answer 1

the gaseous product (NO2) represents the change in mass
... it does not stay in solution in the beaker

the copper stays in solution

Answer 2

The loss in mass is due to the NO2 gas escaping into the atmosphere. It can be the Cu because all of the copper solid left but ended up as Cu(NO3)2. I have no idea what the numbers mean, especially 0s and 118.6s.

Answer 3

oops. typo. It CAN'T be the Cu ----

Answer 4

the "s" data must be elapsed time for the reaction.