Determine the mass of carbon dioxide (in g) produced from the complete combustion of 512.1 g of C8H18 with excess oxygen. Report your answer to the proper number of significant digits without units.

Answer 1

Write this down. It will solve all of them.
Step 1. Write and balance the equation.
2C8H18 + 25O2 ==> 16CO2 + 18H2O

Step 2. Convert what you have (in this case C8H18) into moles.
moles = g/molar mass = 512.1/114.23 = 4.4831

Step 3. Convert moles of what you have (C8H18) into moles of what you want (CO2) by using the coefficients in the balanced equation.
4.4831 mols C8H18 x (16 moles CO2/2 mols C8H18) = 4.4831 x 16/2 = 35.864 moles CO2.

Step 4. Now convert moles to grams.
g CO2 = mols CO2 x molar mass CO2 = ?. Then round the answer to 4 digits.
Post your work if you get stuck. Keep this post handy. It will take care of all of the stoichiometry problems you may have. Use this as a template for other stoichiometry problem.

Answer 2

1578.0