Here's how to determine which reactant will be used up first (the limiting reactant):

1. Balanced Chemical Equation:

You've already provided the balanced equation:

2ZnS + 3O₂ → 2ZnO + 2SO₂

2. Mole Ratios:

The balanced equation tells us the mole ratios of reactants and products:

* 2 moles of ZnS react with 3 moles of O₂

3. Calculate Moles of O₂ Needed:

* You have 1.72 moles of ZnS.

* To use up all the ZnS, you would need (1.72 moles ZnS) * (3 moles O₂ / 2 moles ZnS) = 2.58 moles of O₂

4. Compare Moles of O₂ Needed to Moles Available:

* You need 2.58 moles of O₂

* You only have 3.04 moles of O₂

Conclusion:

You have more O₂ than you need to react with all of the ZnS. Therefore, ZnS is the limiting reactant and will be used up first.