This is a multiple part question, but I only have a question on two parts.
The first part asks that I find the combustion reaction for C3H8, C8H18, and C16H34. I already completed this portion.
Then the second part asks to determine the number of moles of each, in 1000-gram samples.
So my question is that when I find the moles of each, do I find it for one mole of, let's say C8H18, or am I gonna go by the moles of C8H18 in the combustion reaction?
The balanced combustion reaction for C8H18 is 2C8H18+25O2--->16CO2+18H2O
To find the mole of C8H18 in a 1000-gram sample, do I do 1000g C8H18x(1 mol C8H18/114.23 g C8H18)x2 mol C8H18 OR do I just do 1000g C8H18x(1 mol C8H18/114.23 g C8H18)?
Here's the long answer but I need ALL of it so you see where you're going.
Stoichiometry problems are worked this way and you seem to have the steps down very well but just slightly confused about how to do it.
step 1. Wrote the equation. You've done that.
step 2. Balance the equation. You've done that.
step 3. Convert what you're given to moles. You're stuck here.
mols of the C8H18 = grams C8H18/molar mass C8H18 = 1000 g/114 = 8.77 mols.
step 4. Here you convert mols of what you have to moles of what you want. You're confusing moles in step 3 with the conversion step of step 4. Step 4 is where that 2 comes in.
mols C8H18 x (no. mols of what you want/no. moles C8H18) = ?
So that 2 you have goes in the denominator of the conversion factor I wrote on the line above. For example, if you want to know the grams CO2 formed it would be 8.77 mols C8H18 x (16 mols CO2/2 mols C8H18) = 8.77 x 16/2 = ?
step 5. Then convert mols CO2 to grams = mols CO2 x molar mass CO2 = ?
Hope this help. The direct answer to your question is
Yes, you want to determine the mols of C8H18 i 1 mole and not 2 moles. You use the 2 mols to convert from mols C8H18 to mols CO2 generated.