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[font color="#000080"]I'm not sure if i'm right or not.
I'm only making a hypothesis based on my chemistry knowledge.

If you do some equation balacing, you will find out that:
2(NO3) + H2O = 2(HNO3) + O
which is:
Nitrate + Water = Nitric Acid + Oxygen Atom

It does sort of make sense to me.
If my hypothesis is corrent, then nirtate in your aquarium
builds up and reacts with water to form nitric acid, which
kills the fish.

That is not the case. Well i doubt it is.

Water molecules are very tightly bonded, being a covalent bond and all, they naturally are. For a chemical reaction to occur, there needs to be enough energy to pull apart the atoms of the water molecule, and the energy in the reaction you gave would have to come from the electro-negative charge on the nitrate anion, and that is quite a weak force. Therefore the reaction would not occur.

Thats the way i see it.

-- Gomer

I asked my chemistry teacher
the conclusion i got is water molecule can be tear apart and form other molecules
it's called ionise acid/base reaction
water will acts as an acid and donate its proton
my teacher is not so sure about reaction of nitrate,
because nitrate can only acts as an acid but not a base

ughhh I just took the chem regents this is bringing back old memories...

-Formerly known as the Ferretfish

oh---JKW, you cant have Oxygen alone in the pure state like you have in your original equation, it needs to be O2

-Formerly known as the Ferretfish

old tank syndrome is somewhat influenced by a slow accumulation of nitric acid due to excess nitrates. causing a lowering of the pH. thats why regular water changes are good

Water is at a natural equilibrium, it will form the hydronium ion and a hydroxide ion. Both at equal proportions. This is why water has a pH of 7, they equal each other out, one acid, one base. That is what your teacher is getting at.

Something like this..

4H20 <--] 2H3O + 2OH

Old tank syndrome, and nitric acid come about through anaerobic bacterial action, not the water just plainly reacting with nitrate ions. I stand by my explaination above, it just would not happen. It might, but i really doubt it.

-- Gomer

A lowering of ph would be beneficial in my planted tank !
That's it, my excuse to not vacumn is here, thanks Megil !

ps- vacuming up lily pond tab's ain't pretty anyways...

The Amazon Nut...

Interestingly enough, both ammonia, nitrites and nitrates more often than not spend their time in a completely different state, which is dependent (primarily) on pH. That is to say that they all exist in equilibria.
Ammonia exists as either the highly toxic ammonia (NH3) or the relatively harmless ammonium (NH4+). Ammonium dominates below pH7 as the excess protons (or H+, whatever name takes your fancy - you could call it shirley if you so wish) force themselves upon the lone electron pair of the nitrogen in NH3, forming NH4+ (the charge being representative of the charge given to it by the extra proton)
Nitrite (NO2-) exists as either the nitrite ion NO2- or as nitrous acid (HNO2). In this situation, Nitrous acid is present below pH7.
Nitrate (NO3-) exists as either the nitrate ion or as nitric acid (HNO3) in a similar equilibrium to nitrite, ie Nitric and Nitrous acids are present below pH7.

Of course, ammonia/ammonium and nitrites/nitrous acid should only be present during a cycle. As for the nitric acid / nitrate, well, thats why you do water changes. You leave your tank for too long without changing the water, the nitrates build up, the carbonate hardness goes down and boom!, your lovely amazonian set up just crashed, and along with it went all your lovely cardinals and angels.

Now, class, the homework assignments are due in...

oh, just as a further point, a very simplified version of the equation for the reaction between water below pH7 and nitrate ions;

H30+(aq) + NO3-(aq) = HNO3(aq) + H2O(l)

this is a reversible reaction, but i'll be damned if i can find that button on the keyboard <g]

Edit : and dont be thinking that nitric acid is the only reason to do water changes, fish dont JUST poo ammonia. There are also many complex organic acids and many more chemicals.

[span class="edited"][Edited by caled 2004-07-27 18:05][/span]