How can you determine if a sample of gold is pure?

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?

The chemical equation below shows the reaction of sodium (na) and chlorine (cl) to form sodium chloride (nacl). 2na + cl2 → 2nacl in this equation, which of the following is a reactant? i. sodium ii. chlorine iii. sodium chloride

At 20°c, a sample of h2o liquid and a sample of co2 gas each have the same average kinetic energy. why is one a liquid and the other a gas at this temperature?