1. In the reaction 2Ca(s) + O2(g) → 2CaO(s), which species is oxidized?

No, No, No.

The 2 in front of the Ca is a coefficient, not the charge. It is a zero oxidation state because it is a free element. All free elements (those not in a compound) are zero. O2 is zero for the same reason. So Ca goes from zero on the left to 2+ on the right; therefore, it had to lose two electrons to do that which makes Ca oxidized and O2 is reduced.

Well, in this reaction, it's the calcium, Ca(s), that gets really "burned" by the oxygen, O2(g), and turns into calcium oxide, CaO(s). So, the calcium is the one that's getting oxidized here. It's like getting a bad sunburn but on a molecular level.

To determine which species is oxidized in a chemical reaction, you need to identify the changes in oxidation states (also known as oxidation numbers).

In the given reaction, 2Ca(s) + O2(g) → 2CaO(s), we have calcium (Ca) and oxygen (O) participating in the reaction.

The oxidation state of oxygen (O2) is typically -2 in compounds, while the oxidation state of calcium (Ca) is +2 in compounds.

In the reaction, calcium goes from an oxidation state of 0 (since it is in its elemental form) to +2 in CaO. This indicates that calcium has been oxidized because its oxidation state has increased.

On the other hand, oxygen goes from an oxidation state of 0 (since it is in its elemental form) to -2 in CaO. The reduction in the oxidation state of oxygen indicates that it has been reduced.

Therefore, in the given reaction, calcium (Ca) is the species that is oxidized.

i understand!!!!!!! thank you so much. you are awesome

Great!

Oxidation is the loss of electrons.

Ca is zero on the left and +2 on the right. O is zero on the left and 2 on the right.
Which element (Ca or O) lost electrons?

so the answer is O

and how is Ca zero on the left there is a 2 in front of it?