The answer is a conjugate acid.
It is a physical change because only the states as being changes, not the actual bonds in the compound.
The number of moles is simply calculated by taking the ratio of mass over the molar mass. The molar mass of silver nitrate AgNO3 is 169.87 g/mol. Therefore:
number of moles AgNO3 = 100 g / (169.87 g/mol)
number of moles AgNO3 = 0.59 moles
