This question came up on one of our worksheets: A fruity compount A (C2H4O2) is hydrolysed by distilled H2SO4 to give B and C (CH2O2). C reacts with Mg to yield H2 and compound D. B is oxidised to form methanoic acid. Give the structural formula and reaction. Name A, B, C and D. The solution ends up giving the reaction: 2CH2O2 + Mg -> [HCO(O-)]2 Mg2+ (Drawn as an ester except the single bonded O is shown to be negatively charged) + H2 I just thought I'd ask... can someone tell me why we're allowed to show the charge here? The reason I post this not in the homework section is because I want some pointers on where I can look to begin to understand this kind of stuff, rather than just getting help for answering the question. Thank you for any replies.