The basic points in lewis and langmuir theory of electrovalency

The correct answer for the question that is being presented above is this one: "Electrovalency is characterized with the transferring of one or more electrons from one atom to another together with the formation of ions and as well as the number of positive and negative charges. 

The Lewis and Langmuir theory of electrovalency (and as well as Kossel's) is dealing with Ionic bonds. 

Lewis: electron-pair sharing, octet rule, Lewis Symbols or StructureLangmuir: introduced term "covalent" bond, and popularized Lewis's ideas

The Lewis-Langmuir electron-pair or covalent bond is referred as the homopolar bond, where the complete transfer of electrons give rise to ionic, or electrovalent bond (1) through attraction of opposite charges.

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 !