# How do we represent the combustion of ethanol stoichiometrically?

Jan 31, 2017

Balance mass; balance charge.

${C}_{6} {H}_{5} O H + 7 {O}_{2} \rightarrow 6 C {O}_{2} + 3 {H}_{2} O$

#### Explanation:

All hydrocarbons are known to combust to give carbon dioxide and water. So we write the equation accordingly:

${C}_{6} {H}_{5} O H + 7 {O}_{2} \rightarrow 6 C {O}_{2} + 3 {H}_{2} O$

Are charge and mass balanced? For every reactant particle, is there a corresponding reactant particle? If there is not, there should be, and you know that you have furrher work to do. The typical order of operations is: balance the carbons; then balance the hydrogens; and lastly balance the oxygens......

${C}_{6} {H}_{5} O H + {O}_{2} \rightarrow 6 C {O}_{2} + {H}_{2} O$; $\text{carbons balanced.}$

${C}_{6} {H}_{5} O H + {O}_{2} \rightarrow 6 C {O}_{2} + 3 {H}_{2} O$; $\text{hydrogens balanced.}$

${C}_{6} {H}_{5} O H + 7 {O}_{2} \rightarrow 6 C {O}_{2} + 3 {H}_{2} O$; $\text{oxygens balanced.}$

The reaction is now stoichiometrically balanced.

Will this reaction be exothermic? How do you represent the combustion of ethanol, ${C}_{2} {H}_{5} O H$, of hexane, ${C}_{6} {H}_{14}$? The hexane combustion is a trickier proposition on the basis of arithmetic. Try it out.

Especially with aromatics, sometimes incomplete combustion occurs to give $C$, as soot, and $C O$ as combustion products.

For more of the same see here.