I should have been more specific. My chemistry knowledge is not nearly as deep as chem geek's and he is much more thorough and pedagogical in his posts, in short, a very valuable asset to TFP. I often forget that most folks here are not chemistry experts and many would probably rather forget that they ever had to sit through a chemistry class. The key for me in my early chemistry days was to learn that most reactions are equilirium reactions, that is, the arrow in the reaction is a double arrow which means that both the forward (left-to-right) and backwards (right-to-left) reactions are happening simultaneously. I'm a very concrete-thinker and, as such, always want chemical reactions to go one way and to go to completion, kind of like this one -
HCl + NaOH ----> NaCl + H2O
(muriatic acid) + (lye) ---> (salt) + (water)
The truth is that if you could take a snapshot of the solution on a really fine time scale then that reaction actually goes both ways. But, because the forward reaction is so much more energetically favorable and happening at a rate that is so much faster than the backwards reaction, the only thing you ever see is a glass full of salty water. One can certainly stick electrodes in the water and add special separation membranes to turn salt water back into acid and lye, but that takes lots of energy and effort to do and can never really happen completely (ie, you could never turn salt water back fully into acid and lye).
So, whenever you see pool water equations, try to think of it like an equilibrium - there's a forward reaction and a backwards reaction. Then, depending on what we the pool owners do to our water, we bias that reaction in one direction or the other.
