When the equation H2 + Fe3O4 = Fe + H2O is completely balanced using the smallest whole numbers, the coefficient oH2 would be A.) 1 B.)2 C.) 3 D.) 4

Molarity is moles of solute over liters of solution. idk if that is what you are talking about, but you can convert moles of solute to grams of solute using dimensional analyzes by using molar mass found on the periodic table.