Write a balanced equation for the combus- tion of octane, C8 H18, with oxygen to obtain carbon d

Write a balanced equation for the combus- tion of octane, C8...

Key Concepts

Combustion Reaction

A combustion reaction is a type of exothermic chemical reaction in which a substance, usually a hydrocarbon, reacts with oxygen to produce carbon dioxide and water, accompanied by the release of energy in the form of heat and light. This type of reaction is fundamental in fields such as energy production and engine operation.

Balanced Chemical Equation

A balanced chemical equation is a representation of a chemical reaction where the number of atoms of each element is equal on both the reactant and product sides. This balance reflects the law of conservation of mass, ensuring that matter is neither created nor destroyed during the reaction.

Stoichiometry

Stoichiometry involves the quantitative relationships between reactants and products in a chemical reaction. It uses the coefficients from the balanced chemical equation to determine the amounts of substances consumed and produced, playing a critical role in laboratory and industrial chemical calculations.

Mole Ratio

The mole ratio is the proportion between the moles of any two substances involved in a chemical reaction, as derived from the balanced equation. This ratio is essential for determining how much of a reactant is needed or how much product will be formed based on a given amount of another substance.

Transcript

00:01 Okay, we have to balance the equation for the combustion reaction of octane.

00:05 Octane is a liquid, hydrocarbon liquid, right? we're reacting it with o2 to form co2 and h2o.

00:12 So the way that i like to start these is really by starting with adding up all your atoms on both sides, right? so on the left, we have eight carbon atoms, we have 18 oxygen atoms, and we have two oxygen atoms.

00:29 On the right, we only have one carbon atom right now.

00:33 We only have two hydrogen atoms right now, and we have three oxygen atoms.

00:40 So i like to start with the biggest number, the biggest difference, right? so right now that stands out to me to be carbon, right? so why don't we put an eight here? so now we've matched up our carbons.

00:52 So here we go.

00:53 We also change the number of oxygians we have, right? so now we have still only have one for.

00:59 Water but now we have 16 from carbon dioxide so we're going to have 17 hydrogens all together so let's leave oxygen for right now because oxygens in three out of the four chemicals in our entire equation oxygen is probably going to change pretty frequently in these reactions i like to say have oxygen for last right so the other one that sticks out is the amount of hydrogen we have right so we have 18 on the left and only not only two on the right so we're going to put a big old nine here.

01:30 Sorry, i'll do that in red to stay consistent.

01:32 So when we put a nine here, now we change two to 18, because nine times two is 18 hydrogen atoms.

01:39 So carbon and hydrogen are balanced, right, but one thing that changed again is the amount of oxygen that we have.

01:47 So now we have still 16 from the carbon dioxide.

01:50 We're going to add nine more oxygen atoms from the water.

01:57 So there are two things that you can do to get the entire equation to be balanced with 02.

02:05 So your instructor or the textbook might tell you in these combustion reactions to put a fraction coefficient in front of oxygen.

02:15 Right.

02:15 So by doing that, so let's say that i wanted to balance the equation right now.

02:18 So i could put a 25 over 2 here.

02:23 And what that'll do is that will change.

02:32 So when you multiply the coefficient, which is 25 over 2, by the 2 in oxygen, right, the 2's cancel out.

02:41 You're left with 25.

02:42 So that's the fastest way to getting us to balance this equation.

02:45 But if for some reason, so this is a balanced equation, this is an acceptable right answer.

02:51 Right.

02:52 We have eight carbons on both sides...

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