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?

Sn + 4 HNO₃ →  SnO₂ + 4 NO₂ + 2 H₂O

Heating was required to get rid of the H₂O. When all moisture is gone, you weigh the sample. After which, 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.

Hope this helps best of luck :)

Following are the  advantages of the parametric equations: 1) they can be used to graph curves that are not functions, like the unit circle.2) the parameter can be used to represent the quantity that is  useful to  provide us with better information about the graph.3)  it is useful to convert between rectangular equations and parametric equations.with specific reference to chemistry,  parametric equations are employ for solving hydrogen and hydrogen-like ions, quantum mechanically. herein, cartesian coordinates are converted in spherical polar coordinates. the solution obtained, when plotted on spherical polar graph paper, provides visualization of atomic orbital such as s,p,d and f.