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

1 Answer
anor277
Jan 24, 2017

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

#"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_2H_2 rarr 2CO_2#, carbons are balanced;

#HC-=CH rarr 2CO_2 + H_2O#, hydrogens are balanced;

And now balance the equation with respect to oxygens;

#HC-=CH(g) +3/2O_2(g)rarr2CO_2(g) + H_2O(g)#

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 #"ethylene"#, #H_2C=CH_2#; what about #"ethane"#, #H_3C-CH_3#? How does energy transfer in these combustion equations?

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