The balanced chemical equation for the combustion of methane gas CH4 is:CH4 + 2O2 CO2 + 2H2OIn this reaction, methane reacts with oxygen to produce carbon dioxide and water.The oxidation state of carbon in CH4 before the combustion reaction is -4. This is because each hydrogen atom has an oxidation state of +1, and there are four hydrogen atoms bonded to the carbon, resulting in a total oxidation state of -4 for the carbon atom to balance the overall charge of the molecule.After the combustion reaction, the oxidation state of carbon in CO2 is +4. This is because each oxygen atom has an oxidation state of -2, and there are two oxygen atoms bonded to the carbon, resulting in a total oxidation state of +4 for the carbon atom to balance the overall charge of the molecule.