How many molecules of n2 are in a 400.0 ml container at 780 mm hg and 135°c?

Which of these conditions most likely produces an unstable isotope?

In a laboratory, 1.55mg of an organic compound containing carbon, hydrogen, and oxygen is burned for analysis. this combustion resulted in the formation of 1.45mg of carbon dioxide and .89 mg of water. what is the empirical formula for this compound?

Which process describes vaporization that takes place below the surface of a liquid? condensation melting boiling evaporation