Molecular formula for alkane 3-ethyl-2-methylpentane C₈H₁₈, because general formula for alkanes is CₓH₂ₓ₊₂, pentane has five carbon atoms, ethyl group has two carbon atoms and methyl group has one carbon atom. Combustion of alkanes gives carbon(IV) oxide and water as products.
Balanced chemical reaction: C₈H₁₈ + 25/2O₂ → 8CO₂ + 9H₂O or
2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O.