# How do you write a balanced chemical equation for the combustion of C_2H_2?

Jan 24, 2017

Complete combustion of hydrocarbons ALWAYS results in the formation of carbon dioxide and water:

$\text{Hydrocarbon + dioxygen " rarr" carbon dioxide + water}$

#### Explanation:

And when we combust a hydrocarbon, to represent the equation, typically we would balance the carbons, and then the hydrogens, and then the oxygens......so..........

${C}_{2} {H}_{2} \rightarrow 2 C {O}_{2}$, carbons are balanced;

$H C \equiv C H \rightarrow 2 C {O}_{2} + {H}_{2} O$, hydrogens are balanced;

And now balance the equation with respect to oxygens;

$H C \equiv C H \left(g\right) + \frac{3}{2} {O}_{2} \left(g\right) \rightarrow 2 C {O}_{2} \left(g\right) + {H}_{2} O \left(g\right)$

If you like, you can double the entire equation to get rid of the half-integral coefficient. The arithmetic is generally easier if you use it in the given form. The use of half-integral coefficients for binuclear molecules has long precedent.

Can you likewise represent complete combustion of $\text{ethylene}$, ${H}_{2} C = C {H}_{2}$; what about $\text{ethane}$, ${H}_{3} C - C {H}_{3}$? How does energy transfer in these combustion equations?