D. Ratio of Neutrons to Protons
<u>Answer:</u> The mass of iron (II) oxide that contains a million iron atoms is 
<u>Explanation:</u>
We are given:
Number of iron atoms = A million = 
The chemical formula of the given compound is 
It is formed by the combination of 2 iron atoms and 3 oxygen atoms.
According to mole concept:
1 mole of a compound contains
number of particles
1 mole of iron (II) oxide will contain =
number of iron atoms
We know that:
Molar mass of iron (II) oxide = 159.7 g/mol
Applying unitary method:
For
number of iron atoms, the mass of iron (II) oxide is 159.7 g
So, for
number of iron atoms, the mass of iron (II) oxide will be 
Hence, the mass of iron (II) oxide that contains a million iron atoms is 
Answer: The formula of the acid that was neutralized is 
Explanation:
Neutralization is a chemical reaction in which acid and base combine to form salt and water. Acids donate
and bases donate
in water which combine to form water molecules.
As the salt formed is
, the acid must contain
and thus the acid is 
The balanced chemical reaction is ;

The formula of the acid that was neutralized is 