Which of the following is a benefit of having a standard measurement system that can be used by scientists worldwide

I don't see any options, but the benefit of having a standard measurement system that can be used by scientist worldwide, is they are able to read and understand each others work without having to translate it.

Since there is the same amount of agn03 in both silver chloride and silver nitrate they produce the same amount of moles. therefore silver chloride produces the same amount of silver nitrate, so your answer is 15.0 moles of silver nitrate. i hope this !

It will appear as o2(g) as a reactant