Can someone please check-over my Chemistry homework?

Question

In the reaction 2Mg (s) + O₂ (g) + 2H₂O (l) → 2Mg²⁺ (aq) + 4OH^– (aq), which substance is oxidized?

A. Mg

B. O

C. H2O

D. OH

E. None of the Above (This is not a redox reaction.)

 In the reaction 2Mg (s) + O₂ (g) + 2H₂O (l) → 2Mg²⁺ (aq) + 4OH^– (aq), which substance is reduced?

A. Mg

B. O

C. H2O

D. OH

E. None of the Above (This is not a redox reaction.)

In the reaction 2H₂O (l) + 2Cl^– (aq) → H₂ (g) + Cl₂ (g) + 2OH^– (aq), which substance is oxidized?

A. H2O

B. Cl

C. H

D. OH

E. None of the Above (This is not a redox reaction.)

Answer 1

If you answered the first question that Mg was oxidized, and the next question has the same reaction, then something has to be reduced. You cannot have an oxidation without having a reduction.

So, I agree with your answer to #1. Look at the oxygen in #2 and see if the oxidation number doesn't change going from O₂ to OH^-.

Again, in #3, look at the Cl on the left and right side of the equation. Does the oxidation number change? If so, then a redox has occurred. Also look at the oxidation number for hydrogen on the left (in H₂O) and compare it to the oxidation number for hydrogen on the right (in H₂ gas).