Water gas is a synthesis gas, containing carbon monoxide and hydrogen. It is a useful product but requires careful handling due to its flammability and the risk of carbon monoxide poisoning. The gas is made by passing steam over a red-hot carbon fuel such as coke: H2O + C → H 2 + CO (ΔH = +131 kJ/mol) The reaction is endothermic so the fuel must be continually re-heated to keep the reaction going. In order to do this, an air stream, which alternates with the vapor stream, is introduced for the combustion of carbon to take place. O2 + C → CO2 O2 + 2 C → 2 CO (ΔH = −221 kJ/mol) In this case 1 L of O