Write balanced chemical equations for the following reactions:
(i) Oxalic acid is treated with acidified potassium permanganate solution.
(ii) Benzoic acid is treated with a mixture of concentrated nitric acid and concentrated sulphuric acid.
(iii) Methyl magnesium iodide is treated with carbon dioxide and the product hydrolysed in acidic medium.
(iv) Ethylacetate is treated with ammonia.