Stiochiometry

posted by .

Carbon dioxide is released into the air from the combustion of octane (C8H18). How much octane will you need to get 5.00 moles of carbon dioxide? What is the mass of the octane?

• Stiochiometry -

well.... ive got reallly no clue, so anything u say wld help!

• Stiochiometry -

All of these stoichiometry problems are pretty much standard.

Step 1. Write the balanced chemical equation.
2C8H18 + 25 O2 ==> 16CO2 + 18H2O

Step 2. We want 5.00 mols CO2. Convert that to mols C8H18 using the balanced equation.
mols C8H18 = mols CO2 x (2 mols C8H18/16 mols CO2)= xx.
(Note how the unit we don't want cancels --in this case we want mols CO2 to cancel and it does-- and the one we want to keep does not cancel--in this case we want mols C8H18 to remain and it does.) The xx is the answer to the first part of the question.

Step 3. Now we convert mols octane to grams octane remembering that grams = mols x molar mass.
mols octane (from step 2) x molar mass octane = yy grams octane.

Check my work.
Post your work if you get stuck.

• Stiochiometry -

71.25

• Stiochiometry -

When copper(II) oxide is heated in the presence of hydrogen gas, elemental copper and water are produced. What mass of copper can be obtained if 33.8 g copper(II) oxide is used?