Explain how carbon monoxide is produced when petrol is burned in car engines. (2 marks)

Car petrol is usually some form of alkane, which has the general formula C_nH_2n+2. Let us assume we are using Butane (C₄H₁₀). The desired chemical reaction for the complete combustion of butane is 2C₄H₁₀ + 13O₂ --> 8CO₂ + 10H₂O.However, if there is an insufficient supply of oxygen, then there is incomplete combustion, 2C₄H₁₀ + 9O₂ --> 8CO + 10H₂O.As you can see, instead of carbon dioxide given off, the products are water and carbon monoxide, which therefore, results from incomplete combustion.