To balance the half-reaction for the oxidation of ethanol C2H5OH to acetic acid CH3COOH , we need to balance the atoms and charges in the reaction.1. Write the unbalanced half-reaction:C2H5OH CH3COOH2. Balance the carbon atoms:C2H5OH 2 CH3COOH3. Balance the hydrogen atoms by adding H2O:C2H5OH 2 CH3COOH + H2O4. Balance the oxygen atoms by adding H+ ions:C2H5OH + H2O 2 CH3COOH + 4 H+5. Balance the charges by adding electrons e- :C2H5OH + H2O + 2 e- 2 CH3COOH + 4 H+The balanced half-reaction is:C2H5OH + H2O + 2 e- 2 CH3COOH + 4 H+Now, let's determine the oxidation state change of carbon in this reaction. In ethanol C2H5OH , the carbon atom in the CH3 group has an oxidation state of -3, while the carbon atom in the CH2OH group has an oxidation state of -1.In acetic acid CH3COOH , the carbon atom in the CH3 group has an oxidation state of -3, while the carbon atom in the COOH group has an oxidation state of +3.The oxidation state change of carbon in this reaction is from -1 to +3, which is an increase of 4.