MOLES AND MOLECULAR OXYGEN CHEMISTRY HELP PLEASE.

Question

Based on the following chemical equation SO2 + O2 -> SO3 (unbalanced!), h ow many moles of molecular oxygen will be needed for the complete combustion of 100.0 g of sulfur dioxide?

Answer 1

SO₂ + O₂ ==> SO₃ is NOT balanced.  So, before answering the question, one must balance the equation.

2SO₂ + O₂ ==> 2SO₃

Next, find how many moles of SO₂ are present: 100.0 g SO₂ x 1 mole SO2/64 g = 1.5625 moles

From the balanced equation it is seen that it takes 1 moles O₂ for every 2 moles SO₂

Moles O₂ needed = 1.5625 moles SO₂ x 1 mole O₂/2 moles SO₂ = 0.7813 moles O₂ needed (4 sig. figs.)