Mr. Greens answer is good enough as a way of looking at or thinking about it.
The actual answer has to do with ionic strength, in this case until a certain concentration is reached, 0.1M; in this case, water is strong enough to keep the ions apart (without getting too technical we are talking same range of ionic strength). Probabilities as a practical matter play no role (no smart alecks need apply, talking practical application in our aquariums).
This is why we can use “insoluble” substances (CaSO4 for instance) in our aquariums.
Originally Posted by Solcielo lawrencia
Fe would bind to PO4- but only if the Fe is unbound. If it's bound to a chelator, the chelator would prevent it from binding to PO4-.
Hi Solcielo lawrencia, All,
Obviously, the strength of the ligands play a part, but PO4- is really likable. You can try this by making a solution of whichever iron chelates you wish and you choice of phosphates.
In fact varying concentrations, temperatures and pH it is quite easy to see the varying effects.