J.R. S. answered 05/29/22
Ph.D. University Professor with 10+ years Tutoring Experience
2C4H10 + 13O2 ==> 8CO2 + 10H2O ... balanced equation for combustion of butane
Whenever you area given the amounts of BOTH reactants, you MUST first find the limiting reactant.
An easy way to do this is to divide the MOLES of each reactant by the corresponding coefficient in the balanced equation. Whichever value is lowest identifies the limiting reactant. For this problem, we have..
For C4H10: 11.7 g C4H10 x 1 mol C4H10 / 58.12 g = 0.201 mols C4H10 (÷2->0.10)
For O2: 54.6 g O2 x 1 mol O2 / 31.98 g = 1.71 mols O2 (÷13->0.13)
The values of 0.10 and 0.13 are pretty close so they may consider that neither reactant is limiting, but if the math is correct, then since 0.10 is less than 0.13, C4H10 is the limiting reactant.
To find grams CO2 produced, we now use the MOLES of the limiting reactant (0.201 mols C4H10) and the mole ratio in the balanced equation to find mols of CO2, and then convert mols CO2 to grams CO2.
0.201 mols C4H10 x 8 mols CO2 / 2 mols C4H10 = 0.804 mols CO2
0.804 mols CO2 x 44.0 g CO2 / mol = 35.4 g CO2 (3 sig. figs.)