Good evening! This little, nice text about redox reactions I have written today, I will write more tomorrow!
Combustion
Here comes the second redox reaction on this blog. In this one we will have a fuel source to which we will add oxygen, to make a highly exothermic reaction (where heat is made). O2 will either be added from air or from an accelerant. Accelerants make a chemistry reaction to happen faster, because they alter a relevant chemical bond while they become consumed many times in the process. These should not be confused with catalysts, which can be used again and again. The fuel source in a combustion is some kind of hydrocarbon (carbons and hydrogens, C-H, forms the base, and therefore this is an organic compound), and the main products are carbon dioxide and water as steam. O2 can also combine with an element or compound that is inorganic (here we don’t find a carbon-hydrogen bond), but this kind of oxidation-reduction reaction will not be equally combustible, and the product will not be CO2 and H2O. (If you for example think of Mg + O2 ---> MgO + some light and heat.)
If we use wood as a fuel then activated carbon will be formed. The formula for that is C7H4O and it can be used for gunpowder, which is the earliest known explosive. More about charcoal is that you can for example fertilize your garden with it, and it is absorbing toxins and make the ground more alkaline. But now let’s talk about other hydrocarbons also. Three very popular fuel sources are butane, C4H10, propane, C3H8 and octane, C8H16. Butane is an alkane (saturated hydrocarbons that have only single bonds) that is a gas at room temperature, that is denser than air. In the chemical reaction we will get CO2 and H2O as products when there is a lot of oxygen involved, otherwise the products will be carbon monoxide, CO, and H2O. When oxygen is limited as in the last reaction, it will occur an incomplete combustion. Butane can be used for example gasoline blending and end up in a spark-ignited engine. The user will use a spark plug so the air and fuel get the energy of activation to overcome an inert state. Then combustion is on.
Now we will talk about the subcategories in this process. There can be a complete combustion, when the reactant is used up completely during the chemical reaction. This almost never happens in nature, only in engines. The reaction is possible at high availability of O2. This redox reaction in question can also happen during an incomplete combustion. Here the O2 can only consume the hydrocarbons partly, and the products will be the poisonous carbon monoxide gas, CO, H2O and soot, C. Hydrogen reacts first with the air, and carbons gets the leftovers if there are any. During a complete combustion we see a blue flame, otherwise it’s yellow, thanks to all the glowing carbon. Why do you get an incomplete combustion? It can happen for example if there are many impurities among the reactants. We can also be talking about a fuel/surface/compound that is not very flammable. Therefore we get this soot and CO gas. CO is poisonous because it makes the hemoglobin useless for O2 transport. It takes its place in the body.
Add comment
Comments