The citizens of the world burn the fossil fuel equivalent of...

The citizens of the world burn the fossil fuel equivalent of 7 * 10^12 kg of petroleum per year. Assume that all of this petroleum is in the form of octane (C8H18) and calculate how much CO2 (in kg) the world produces from fossil fuel combustion per year. (Hint: Begin by writing a balanced equation for the combustion of octane.) If the atmosphere currently contains approximately 3 * 10^15 kg of CO2, how long will it take for the world's fossil fuel combustion to double the amount of atmospheric carbon dioxide?

Transcript

00:01 So for the first part of this question, we're asked to find how much carbon dioxide is produced per year, assuming that all of the octane is produced.

00:15 So first, i wrote the combustion reaction for octane.

00:20 And then first we have to balance this equation in order to do the rest of the steps.

00:26 So when we're balancing the equation, we have eight carbons on the left.

00:30 So we're going to put an eight coefficient from the carbon dioxide.

00:33 So now we have the same number of carbons on each side.

00:37 On the left, we have 18 hydrogens, and we only have two on the right.

00:41 So if we put a nine here, now we have 18 hydrogens on each side.

00:46 Now let's square up our oxygens.

00:49 So we have 16 oxygens here and nine oxygens here for a total of 25 oxygens.

00:56 We have two over here.

00:57 Remember, an easy cheat for the oxygen.

01:02 We can just do 25 over 2.

01:05 Now we have the same number of carbons, hydrogens, and oxygens on each side, and our equation is balanced.

01:14 So when we are converting the kilograms of octane into kilograms of carbon dioxide, first we need to convert kilograms to grams.

01:26 Then we use the molar mass to convert grams to moles.

01:29 Then we can compare moles using the coefficients from the balance equation, and then convert the moles of carbon dioxide into kilograms.

01:40 So this is going to be a lot of steps.

01:45 So first, if we start out with seven times 10 to the 12 kilograms of c8, h18, or octane for every one year, we convert this to grams, so that way, because molar mass is in grams to moles, so we have 1 ,000 grams for every 1 kilogram, and then times the molar mass of octane, so 8 times the molar mass of 1 carbon, which is 12, plus 18 hydrogens.

02:30 It's going to have a molar mass of 114 .2.

02:36 So for every one mole of octane, we have 114 .2 grams of octane.

02:47 All right, so now we have moles of octane, and so then we want to convert this into moles of carbon dioxide.

02:52 So we look at the coefficients.

02:58 So we have eight moles of carbon dioxide for every one mole of octane.

03:09 Now we convert moles of carbon dioxide into kilograms.

03:12 So we take this times the molar mass of carbon dioxide, which is 44 .01 grams per mole.

03:19 So 44 .01 grams of carbon dioxide for every one mole of carbon dioxide...