What is a hydrocarbon?
It's a compound of carbon and hydrogen and no other element.
What is an incomplete combustion?
It's a reaction with the oxygen gas present in air which produces carbon and water.
What is an complete combustion?
It's a reaction with the oxygen gas present in air which produces carbon dioxide and water.
Write down the formula of incomplete combustion of methane!
$CH_4$ $+$ $O_2$ $\rightarrow$ $C$ $+$ $2H_2O$.
Write down the formula of complete combustion of methane!
$CH_4$ $+$ $2O_2$ $\rightarrow$ $ CO_2$ $+$ $2H_2O$ .
Write down the formula of incomplete combustion of hexane!
$2C_6H_{14}$ $+$ $7O_2$ $\rightarrow$ $ 12C$ $+$ $14H_2O$.
Write down the formula of complete combustion of hexane!
$2C_6H_{14}$ $+$ $19O_2$ $\rightarrow$ $ 12CO_2$ $+$ $14H_2O$.