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Combustion Reactions.

Posted: Wed Oct 03, 2018 1:58 pm
by gabbym
In example H1 from the Fundamentals H section of the seventh edition, you are asked to write and balance the chemical equation for the combustion of liquid hexane, C6H14, to gaseous carbon dioxide gas and gaseous water. I understand that the liquid hexane needs to react with something in order for it to be able to combust, but will O2 always be used? For example, if we were asked to write and balance the chemical equation for the combustion of another compound, would we always add 02?? Sorry for the super basic chemistry questions, my high school chem class didn't teach me anything :(

Re: Combustion Reactions.

Posted: Wed Oct 03, 2018 2:06 pm
by cristinapadilla_1E
O2 will always be one of the reactants and the products will always be H2O and CO2.

Re: Combustion Reactions.

Posted: Wed Oct 03, 2018 2:22 pm
by Amy Dinh 1A
Yes, Oxygen is always needed for a combustion reaction to occur, and the products will always have CO2 and H2O.

Re: Combustion Reactions.

Posted: Wed Oct 03, 2018 2:56 pm
by Katie_Duong_1D
The most basic combustion reactions involve a hydrocarbon and oxygen to create water and carbon dioxide. In this case, oxygen is the oxidant.

Example H1 asks to balance the combustion reaction of C6H14. I would start off with C6H14 + O2 --> H2O + CO2. From there, balance the carbons; since there are 6 C atoms on the left, write a 6 in front of CO2 on the right.

C6H14 + O2 --> H2O + 6CO2

Now the hydrogens need to be balanced. There are 14 H atoms on the left, so write 7 in front of H2O.

C6H14 + O2 --> 7H2O + 6CO2

Now the oxygen atoms need to be balanced. There are 2 O atoms on the left and 19 O atoms on the right. Write 19/2 in front of O2 on the left, so there are 19 O atoms on each side.

C6H14 + 19/2O2 --> 7H2O + 6CO2

This equation is balanced. However, we want to get whole number stoichiometric coefficients. Multiply the entire equation by 2.

2(C6H14 + 19/2O2 --> 7H2O + 6CO2) = 2C6H14 + 19O2 --> 14H2O + 12CO2

Re: Combustion Reactions.

Posted: Wed Oct 03, 2018 3:03 pm
by Kayla Vo 1B
As said in the previous posts, the products of a complete combustion are always CO2 and H2O. However it's also good to keep in mind that during an incomplete combustion (not enough oxygen is provided for the reactant to completely burn) other products, such as C and CO (carbon monoxide), can also be formed as a result. But in most combustion problems it is inferred that the reaction is complete unless otherwise stated.

Re: Combustion Reactions.

Posted: Wed Oct 03, 2018 3:10 pm
by Karla_Ocampo 4E
Hi Gabby!
Dont even apologize! My high school chemistry class didn't teach me anything either so same. So to answer your question, combustion problems will always need O2 as a reactant and H2O and CO2 as the products. Then you just continue to balance the equation and so on. I hope this helped!

Re: Combustion Reactions.

Posted: Wed Oct 03, 2018 3:11 pm
by Mikka Hoffman 1C
In combustion reactions, the reactants are always O2 and the hydrocarbon and the products are CO2 and H2O.

Re: Combustion Reactions.

Posted: Wed Oct 03, 2018 3:39 pm
by katie_sutton1B
To add onto this question, does it matter which order we put CO2 and H20 as the products? For example, can we write C6H6 + O2 --> H20 + CO2, or does it have to yield CO2 + H2O?

Re: Combustion Reactions.

Posted: Wed Oct 03, 2018 3:46 pm
by Angela Grant 1D
In response to the most recent comment: no, it does not matter which order products or reactants are written in, as long as they are on their respective sides of the chemical equation (reactants on left, products on right)

So the equation can be written as C6H6 + O2-> H2O + CO2