The difference is the mass of the gases that were formed during the reaction. If the cup is open, it is always the case that the gas would escape. Any reaction that forms a gas as a product is called a gas forming reaction.
The Chemica formula of the product is Na2S which is called sodium sulfide. remember that sodium is a metal and all compounds containing a metal are named with the stock system.
Describe the process by which Ag+ ions are precipitated out of solution. 4. In your testing, several precipitates are formed, and then dissolved as complexes.
