[greenbathtub]

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  Am really excited to find your excellent site. I have been searching for an
answer for so long and have found no good help.  It is a chemistry
question although I am not a chemist, I feel I would know the answer if I were
a Chemist.  --
  We have a rainwater storage tank for our drinking water which we put
through a carbon filter before use.  My question is when you have H NO3
and you soak Carbon in it, what would the chemical result be? I know
that is assuming that there are no other chemicals present in the rain -
like sulphur, or metals from the roof catchment, or sugars from the
dissolved leaves and such,  etc. If you cannot tell me the answer, could
you tell me where I can get help?  I know I can get a standard water
test done for $200 but this will not tell me the compounds that are
present - and this is what I want to know.  Look forward to your reply.

[vhpk]

4HNO₃ + C --> CO₂ + 4NO₂ +2 H₂O

[AWK]

HNO3 + C --> C6(COOH)6 + NO2 +H2O
Melitic acid can be obtained

[greenbathtub]

Thank you vhpk for your reply.  OK, I will accept that I am way out of my depth here, but this raises a further question: 
The result you gave is that it takes four HNO3 s to make the resulting set. When you mathematically add the numbers (i.e. four times O3, in the HNO3 is 12 oxygens etc.) or as in the following sum -
  question:            4 x C+HNO3 = 4 x C / 4 x H / 4 x N / 12 x O.
  result:    CO2 + 4NO2 + 2H2O = 1 x C / 4 x H / 4 x N /  5 x O.),
  this leaves Cx3 + Ox7 loose, which would reduce to 3 x CO2 + 1xO.
Since we can't match the oxygen to anything. My new question is, does this leave an unmatched oxygen molecule in the mix - and is this called a free radicle?

Wow, did that take some lateral thinking to sort out how to explain the thoughts!!!! Hope I am not too dense for you. Would appreciate your kindest answer, ....thanks.

[greenbathtub]

Thank you also AWK for your reply re Melitic acid.  Went to reference books but could only find Mellitic acid - trust they are the same.  It says this is a crystalline substance - would there be evidence of this on, say the sides of the tank? Or left on glass after evaporation of water?

[enahs]

Greenbathtub, the number in front (the stoichiometric coefficient) only applies to the chemical species it is directly in front of.
So that "4 HNO₃ + C " there is only 4 HNO₃ and 1 C. If there is no number in front of a species, 1 is implied.
Knowing that, your math should work out now!

[greenbathtub]

Thanks enahs. An over estimation by a novice - that was about the fourth time I had tried to check.  So I have re-done my maths and found this:-

question:                 C+HNO3 = 1 x C / 4 x H / 4 x N / 12 x O.
result:    CO2 + 4NO2 + 2H2O = 1 x C / 4 x H / 4 x N /  5 x O.

So don't I now have seven loose oxygen molecules? Wow, if they are free and radicle, the water tank would be a great place to party with all those wild things.

Maybe I should explain my thoughts about the suggested results, before I look like a complete goose.  I am aware that oxygen (along with NO2 and CO2) is a gas and should escape the mix.  The reason I discounted this is that I consider the tank to be pretty well a closed vessel - and not open as in a glass or cup.  I know gas does not go too far in it.  Once we had to buy town water when we ran out of rain.  The smell of the chlorine was so strong when you walked by, it would take your breath away.  This smell remained in the tank for a long time as the water was used, and even after a little bit of subsequent rain had  gone into the tank (I did expect that the acidity of the rain would exhaust it).  Chlorine disappears really quickly from an open vessel but in this case it just stayed in the tank.

So is it possible that this is a stable mix that will remain as the result is?

[AWK]

Thank you also AWK for your reply re Melitic acid.  Went to reference books but could only find Mellitic acid - trust they are the same.  It says this is a crystalline substance - would there be evidence of this on, say the sides of the tank? Or left on glass after evaporation of water?

Mellitic acid (double l is correct) can be obtained by oxidation of carbon using warm concentrated nitric acid.
Oxidation by nitric acid always form NO or NO2 (depending on its concentration). Diluted nitric acid rather does not oxidate carbon.

[woelen]

Nothing happens, when C is added to HNO3, which may be present in rain-water at VERY strong dilution.

All the kind of reactions, discussed above may occur, when carbon comes in contact with concentrated acid, but believe me, none of these will occur in a rain-water storage tank.

The same is true for any sulphuric acid or sulphurous acid, which may be in the water in trace amounts. It does not react with the carbon at such strong dilutions.

Of course, there could be bad chemicals in that water (e.g. stuff from the roof, dissolved metal salts from atmospheric dust, etc.), but I would not worry about reactions with the carbon in the filters.

[greenbathtub]

Thank you all for your responses and so fast.  Thank you woelen for the most recent.  I keep getting told that no reaction will happen in a rainwater storage tank. So far no one has told me WHY it can't happen -- if it happens  in a lab, it is possible that
(a) the temperature here is right or
(b) that (in a hot climate, the trees about can expire more CO2) the pH is just a fraction lower than normal - average is 5.8 but here we find 5.4 rather constant or
(c) that there is some quirk happening here that does cause an absorption or reaction. 

I have looked in so many places that produce drinking water guidelines and I can find no information on tank water and what happens when a carbon filter is used. I cannot even find where anyone has actually looked at this.
   When we bought the filter, we were assured that it could not alter the pH of our water.  We checked other authorities rather than taking the vendor's word for it and they all seemed to agree - no change.  We installed the filter and - guess what - instant raising of the pH. This lasted for a week or so and then went back to usual.  I understand that that means the activated carbon was no longer active.  The fact remains that it DID change the pH. Maybe you can understand why my faith in "it can't happen" is rather shaken.

You mentioned sulph acids.  I have also looked at formic (from the trees and biota in the tank) and others but cannot eliminate any. I also realise that there could be metals from the zincalum roof and copper from the water pipes - even the reaction of amalgam tooth fillings with the acidic H NO3. These things are all rather standard things for most people on rainwater.  The only difference is that not many have a carbon filter ( a few have a carbon filter when they have a cement tank and different pH of their water) - since activated carbon is mainly to get chlorine gas out.

So I look forward to hearing if anyone wants to take this further.