78.0 g of H2O will react with Fe to produce formula units of FeO2
Please help

1.306 × 10^24 formula units.

Explanation:

The chemical equation of this qkrstios as follows:

Fe + 2H2O → FeO2 + 2H2

Based on the reaction, 2 mole of H2O produces 1 mole of FeO2

Using the formula as follows;

Mole = mass/molar mass

Molar mass of H2O = 1(2) + 16 = 18g/mol

mole = 78/18

mole = 4.33moles

If 2 mole of H2O reacts to produce 1 mole of FeO2

4.33 moles of H2O will produce 4.33/2 = 2.17moles of FeO2.

To convert moles to formula units, we multiply number of moles by Avagadro number (6.02 × 10^23 units)

= 2.17 moles × 6.02 × 10^23 units

= 13.06 × 10^23

= 1.306 × 10^24 formula units.

it's all four options.