Question

Can someone explain to me how to do this? Consider the following equation: 2ZnS + 3O₂ ---> 2ZnO + 2SO₂ , ΔH° = - 878.2kJ. How much heat is released when 3.0 mol ZnS reacts in excess oxygen?

Answer 1

The reaction of 3.0 mol of ZnS releases 1300 kJ.

We can write the equation as

2ZnS + 3O₂ → 2ZnO + 2SO₂ + 878.2 kJ

Then we can use a conversion factor as follows.

3.0 mol ZnS × `(878.2"kJ")/(2"mol ZnS")` = 1300 kJ

Note: The answer can have only 2 significant figures, because that is all you gave for the moles of ZnS. If you need more precision, you will have to recalculate.

Hope this helps.