The first statement (Matter is neither created nor destroyed) is correct.
The second statement would violate the law of conservation of mass (I will refer to this as LCM), as it would mean matter can "flow" into the universe, but not out, meaning the total matter will never be less than it was before.
The third statement violates LCM because it means matter is created during a reaction, which is not true.
The last statement violates LCM because it means matter is lost during a reaction, which is not true.
Answer:
Since there are 3 Hydrogen atoms present, the formula mass of H is 1.0 × 3 = 3.0 g/mol. Therefore, by adding them up, the formula mass of ammonia is: [14.0 g/mol + 3.0 g/mol] = 17.0 g/mol.
