January 2019 NY Regents Chemistry Exam
34 What is the formula for iron(II) oxide?
(1) FeO
(2) FeO2
(3) Fe2O
(4) Fe2O3
Solution: This compound consists of a metal (iron) with a nonmetal (oxygen). The roman number represents the oxidation number (charge) of iron. The oxidation number of oxygen is on the Periodic Table and is -2.
Each element gives the oxidation number to its' partner for the correct formula.
Fe^2+ O^2-
Fe2O2 = Fe1O1 or FeO
Answer: 1
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