Why is pcl3 called phosphorus trichloride

P is the chemical symbol for phosphorus.
Cl is the chemical symbol for chloride, and there are three of them - the prefix for three is tri-.

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 !