4FeS2 + 11O2 yields 2Fe2O3 +8SO2. I don't understand this equation. FeS2 leads me to believe that the Fe here has a charge of +2 but in the product it appears to have a charge of +3 judging by the formulas. How is this possible and what is this equation representing?

You have written an oxidation-reduction kind of equation. They are VERY common. And your perception is correct, Fe has gone from an oxidation state of +2 to an oxidation state of +3. It makes that move by losing electrons and that is defined as oxidation (the loss of electrons). If something is oxidized, something else must be reduced. What is it in this equation? O2 goes from an oxidation state of zero on the left to -2 on the right, which is a gain of electrons and that is defined as reduction. I hope this helps.

The equation you provided represents a balanced chemical equation for the reaction between iron sulfide (FeS2) and oxygen (O2) to produce iron(III) oxide (Fe2O3) and sulfur dioxide (SO2).

To understand why iron in FeS2 appears to have a different charge in the product (Fe2O3), let's look at the oxidation numbers. The oxidation number of sulfur (S) is -2 in FeS2 since it is in the sulfide ion. Let's assume the oxidation number of iron (Fe) in FeS2 is x:

FeS2: x + (-2) * 2 = 0
x - 4 = 0
x = +4

From this, we can see that the charge on iron in FeS2 is +4.

In the product, Fe2O3, the oxidation state of oxygen is -2. Let's assume the oxidation state of iron in Fe2O3 is y:

Fe2O3: 2y + (-2) * 3 = 0
2y - 6 = 0
2y = +6
y = +3

So, in Fe2O3, the iron has an oxidation number of +3.

The difference in oxidation states can look confusing, but it is due to the different compounds formed in the reaction. Iron in FeS2 is in its +4 oxidation state, and during the reaction, it is oxidized to +3 in Fe2O3 while sulfur in FeS2 is reduced to sulfur dioxide (SO2).

Overall, this equation represents a chemical reaction in which iron sulfide reacts with oxygen to produce iron(III) oxide and sulfur dioxide. It is important to note that the balanced equations provide information about the reactants and products in terms of their formulas and stoichiometry. The oxidation numbers of the elements help determine how electrons are transferred or shared in a reaction.