31. The mass number of a nucleus is : a) always less than its atomic number: b) the sum of the number of protons and neutrons present in
the nucleus; c) always more than the atomic weight; d) a fraction.

Ibelieve its a because an empirical formula usually has a ch in it your options are a or b

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 !