You need to make 30 grams of CO2, how many grams of C3H8 are needed?

Question

C3H8 + 5 O2 → 3 CO2 + 4 H2O

I just need a little more help trying to understand

Answer 1

C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O ... balanced equation

From this balanced equation, it tells us that 1 mole of C₃H₈ produces 3 mols of CO₂. So, if we know how many moles of CO2 are produced, we can figure out how many moles of C₃H₈ were used. Right?

So, let us convert 30 grams of CO2 to moles of CO2, and then we can find the moles of C₃H₈ and from that, we can find the grams of C₃H₈. Remember, in stoichiometry we always deal in MOLES, not in GRAMS.

Moles of CO2 produced:

30 g CO2 x 1 mol CO2 / 44 g = 0.682 moles CO2

Moles C₃H₈ needed:

0.682 mols CO2 x 3 mols CO2 / 1 mol C₃H₈ = 2.05 mols C₃H₈

Grams C₃H₈ needed:

2.05 mols C₃H₈ x 44.1 g C₃H₈ / mol = 90.2 g C₃H₈ needed