A chemical change Is any change that results in the formation of new chemical substances .
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<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 
71.8 g of iron (III) oxide (Fe₂O₃) were produced from 3 moles of magnesium oxide (MgO).
Explanation:
We have the following chemical reaction:
2 FeCl₃ + 3 MgO → Fe₂O₃ + 3 MgCl₂
We see from the chemical reaction that 3 moles of magnesium oxide (MgO) will produce 1 mole of iron (III) oxide (Fe₂O₃).
number of moles = mass / molar weight
mass = number of moles × molar weight
mass of Fe₂O₃ = 1 × 71.8 = 71.8 g
Learn more about:
number of moles
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