A bottle of an unknown liquid has a volume of 6.3 mL and mass 255.15 g. What is its density?

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?

Find the mass, in grams, of 5.00*10^23 molecules of f2

One student said that the investigation was not valid (a fair test). write a plan for the investigation that includes improvements to the method and apparatus