To determine the number of moles of oxygen (O2) produced by 1.2 mol of KClO3, we need to consider the balanced chemical equation for the decomposition of KClO3:

2KClO3(s) → 2KCl(s) + 3O2(g)

According to the equation, 2 moles of KClO3 produce 3 moles of O2. So, we can set up a proportion to find the moles of O2 produced by 1.2 mol of KClO3:

(Moles of O2 produced) / (Moles of KClO3) = (3 mol O2) / (2 mol KClO3)

Cross-multiplying to solve for the moles of O2 produced:

(Moles of O2 produced) = (1.2 mol KClO3) * (3 mol O2 / 2 mol KClO3)

(Moles of O2 produced) = 1.8 mol O2

Therefore, 1.2 mol of KClO3 would produce 1.8 mol of oxygen (O2).