Calculate the number of grams

Question

Sulfur trioxide gas can be synthesized by the reaction of sulfur dioxide gas and oxygen gas. Calculate the number of grams of sulfur trioxide gas that can be made by reacting 15.7 grams of sulfur dioxide gas in the presence of excess oxygen gas.

Answer 1

Hello, Ana,

The first thing we need is a balanced equation for this reaction. I come up with:

2SO₂ + 1O₂ = 2SO₃

This tells us we'd expect to get two mole of sulfur trioxide for every two moles of SO₂, for a 1:1 molar ratio. Now we should find the number of moles contained in 15.7 grams of sulfur dioxide by dividing the mass by the molar mass of the compound (15.7g/64.1g/mole) = 0.245 moles SO₂. That means we'll get (on a good day) the same number of moles of SO₃, since we have excess oxygen (more than enough). Convert moles SO₃ to grams by multiplying by sulfur dioxide's molar mass:

(0.245 moles SO₃)*(80.1 g/mole) = 19.6 grams SO₃

I hope this helps,

Bob