I have attached a solution to one of my homework questions that states "Draw hydrogen bonds that might be formed between a water molecule and the following compounds: a) H3PO4; b) PO43-; c) aniline; d) pyridine; e) ethylamine; f) ethyl ammonium ion; g) acetic acid."
My question is specifically for H3P04 and Acetic acid. Why is it that in H3PO4, the H on the OH makes the hydrogen bond with the O of a water molecule, but in acetic acid, the lone electron pair on the OH makes the hydrogen bond with the H of a water molecule.
Does it make a difference if I instead drew a hydrogen bond from the lone electron pair of the OH on H3PO4 and connected this to the H of water? Is it the same thing or is there a reason these are like this?