What are two things that you observed when you heated the mixture of tin and nitric acid over the bunsen burner in the virtual lab, and why was it necessary to heat the mixture in order to determine the empirical formula?

1. The reaction for this would be:

Sn + 4 HNO₃ →  SnO₂ + 4 NO₂ + 2 H₂O

The first observation would be bubbling of the solution and brown acrid smoke is produced due to the presence of NO₂ gas. Another observation would be the presence of a white solid which is SnO₂.

2. Heating was required to get rid of the H₂O. When all moisture is gone, you weigh the sample. Afterwhich, you further heat it to get ride of the oxygen. By doing this, you would know the individual mass of each element. Then, you can solve for the empirical formula of the oxide of tin.

Remember that rust prevented by placing a sacrificial electrode in electrical contact with the iron. the sacrificial electrode must be composed of a metal that  oxidizes  more easily than iron (that is, it must be below iron in table 18.1).