Why the size of atom does not decrease regularly in a period.

When atomic number increases there will be an increase in concentration of positive charges in the nucleus. The valence shell electrons are attracted by the nucleus/ protons when we gradually increase the atomic number. So the size would be less if the valence shell will contract because of the strong attraction of the nucleus. 

Ithink is d. physical property

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 !