Question

which has the highest and lowest energy value, and why: Ethanol, Butanol and Octanol?

Answer 1

Octanol is highest, Ethanol is lowest. With each Carbon atom added, there are more chemical bonds that need to break in the Combustion reaction. (I'm assuming you're talking about heat of combustion energy.)

Answer 2

Alcohols are organic, and each one has its own formula. In this experiment we have used Ethanol, Propanol, Butanol, Pentanol Hexanol, Heptenol, and Octanol. Alcohols react with oxygen in the air to form water and carbon dioxide. The reaction that is involved in burning alcohols is exothermic because heat is given out. Form this reason the reactant energy is higher than that of the product. Ethanol, (C2H5OH) Propanol, (C3H7OH) Butanol, (C4H9OH) Pentanol, (C5H11OH) Hexanol, (C6H13OH) Heptanol, (C7H15OH) Octanol, (C8H17OH) When these alcohols are burnt they show a trend that the fewer the bonds the less energy is released, so the more bonds the more energy is released. Alcohols are good to use in this experiment because they burn easily and all have simular chemical formulas.

Answer 3

As mhbretrz said, you can see the trend from the molecular structures given above that Ethanol has two carbon atoms, Butanol has four carbon atoms and Octanol has eight caron atoms.
so Ethanol < Butanol<Octanol